CVE-2023-6184: Citrix Virtual Apps And Desktops XSS Flaw

CVE-2023-6184 Overview

CVE-2023-6184 is a Cross-Site Scripting (XSS) vulnerability affecting Citrix Session Recording, a component of Citrix Virtual Apps and Desktops. This vulnerability allows an authenticated attacker with high privileges to inject malicious scripts into the Session Recording application, potentially compromising the security of user sessions and sensitive session data within enterprise Citrix environments.

Critical Impact

Successful exploitation could allow attackers to execute arbitrary scripts in the context of authenticated users, potentially leading to session hijacking, credential theft, or further compromise of the Citrix infrastructure.

Affected Products

• Citrix Virtual Apps and Desktops (Current Release versions prior to the fix)
• Citrix Virtual Apps and Desktops 1912 LTSR (CU1 through CU7)
• Citrix Virtual Apps and Desktops 2203 LTSR (CU1 through CU3)

Discovery Timeline

• January 18, 2024 - CVE-2023-6184 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-6184

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-913 (Improper Control of Dynamically-Managed Code Resources). The Cross-Site Scripting flaw exists within the Citrix Session Recording component, which is used to capture, catalog, and archive user sessions for auditing, compliance, and troubleshooting purposes.

The vulnerability requires an attacker to have high-level privileges on the system, indicating that some form of initial access or administrative credentials would be necessary for exploitation. However, once these prerequisites are met, the attacker can inject malicious scripts that execute in the browser context of other users accessing the Session Recording interface.

Given that Session Recording is typically used by administrators and security personnel to review sensitive user sessions, successful exploitation could expose highly sensitive information including user activities, credentials entered during recorded sessions, and potentially confidential business data.

Root Cause

The root cause stems from improper input validation and sanitization within the Citrix Session Recording web interface. User-supplied input is not adequately filtered or encoded before being rendered in web pages, allowing malicious script content to be executed in the browsers of other users who view the affected content.

Attack Vector

The attack is network-accessible, meaning an authenticated attacker with high privileges can remotely exploit this vulnerability without requiring user interaction. The attacker would inject malicious JavaScript or HTML content through input fields or parameters within the Session Recording interface. When other administrators or users view the affected content, the injected scripts execute in their browser context, potentially allowing:

• Theft of session cookies and authentication tokens
• Capture of keystrokes and sensitive data entered in forms
• Redirection to malicious sites
• Modification of displayed content to deceive users
• Execution of actions on behalf of the victim user

The vulnerability mechanism involves insufficient sanitization of user-controlled input within the Session Recording web interface. When malicious content is stored and later rendered to other users, the browser interprets the injected scripts as legitimate code, executing them with the full privileges of the viewing user's session. For detailed technical information, refer to the Citrix Security Bulletin for CVE-2023-6184.

Detection Methods for CVE-2023-6184

Indicators of Compromise

• Unusual JavaScript or HTML content in Session Recording database entries or log files
• Web server logs showing attempts to inject script tags or encoded JavaScript through Session Recording parameters
• User reports of unexpected pop-ups, redirects, or behavior when accessing the Session Recording interface
• Evidence of session cookie theft or unauthorized access following Session Recording usage

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block common XSS attack patterns targeting the Session Recording application
• Monitor HTTP request and response logs for suspicious script injection attempts or encoded payloads
• Deploy endpoint detection and response (EDR) solutions like SentinelOne to identify malicious browser activity resulting from XSS exploitation
• Enable Content Security Policy (CSP) headers and monitor for CSP violation reports

Monitoring Recommendations

• Configure alerting for unusual administrative activity within Citrix Session Recording
• Monitor for new or modified scripts within the Session Recording web application directories
• Implement logging and analysis of user interactions with the Session Recording interface
• Review authentication logs for suspicious privileged access patterns preceding potential exploitation attempts

How to Mitigate CVE-2023-6184

Immediate Actions Required

• Apply the security patches provided by Citrix immediately for all affected versions
• Restrict administrative access to the Session Recording component to only essential personnel
• Review audit logs for any indicators of prior exploitation attempts
• Implement network segmentation to limit access to the Session Recording management interface

Patch Information

Citrix has released security updates to address this vulnerability. Organizations should update to the latest available versions:

• For Current Release deployments: Update to the latest Current Release version
• For 1912 LTSR: Apply the latest cumulative update that addresses CVE-2023-6184
• For 2203 LTSR: Apply the latest cumulative update that addresses CVE-2023-6184

Detailed patch information is available in the Citrix Security Bulletin CTX583930.

Workarounds

• Limit network access to the Session Recording interface using firewall rules or network segmentation
• Implement strict Content Security Policy (CSP) headers to prevent inline script execution
• Conduct regular security audits of user accounts with administrative privileges to Session Recording
• Consider temporarily disabling the Session Recording feature if immediate patching is not possible and the functionality is not critical

# Example: Restrict access to Session Recording using Windows Firewall
# Block external access to Session Recording ports
netsh advfirewall firewall add rule name="Block External Session Recording Access" dir=in action=block protocol=tcp localport=443 remoteip=any

# Allow only specific management network
netsh advfirewall firewall add rule name="Allow Management Network Session Recording" dir=in action=allow protocol=tcp localport=443 remoteip=10.0.0.0/8