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. The flaw allows an authenticated attacker with high privileges to inject and execute arbitrary script content within the application context. Citrix has assigned the issue to CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-913 (Improper Control of Dynamically-Managed Code Resources).

Critical Impact
Successful exploitation allows attackers to compromise confidentiality, integrity, and availability of the Session Recording environment, with EPSS scoring placing this vulnerability in the 95th percentile for exploit likelihood.

Affected Products

Citrix Virtual Apps and Desktops 1912 LTSR (including CU1 through CU7)
Citrix Virtual Apps and Desktops 2203 LTSR (including CU1 through CU3)
Citrix Session Recording component within Citrix Virtual Apps and Desktops

Discovery Timeline

2024-01-18 - CVE-2023-6184 published to NVD
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-6184

Vulnerability Analysis

The vulnerability resides in the Citrix Session Recording component bundled with Citrix Virtual Apps and Desktops. Session Recording captures user activity within published applications and desktops for compliance and forensic purposes. The component fails to properly neutralize attacker-controlled input before rendering it within its web interface.

An attacker with high privileges on the network can supply crafted payloads that the application reflects or stores without sanitization. When a target user loads the affected resource, the injected script executes within their browser session under the trust boundary of the Session Recording application.

The CWE-913 classification indicates the flaw extends beyond standard reflected XSS into improper control of dynamically managed code resources. This expands the attack surface to scenarios where injected content influences server-side script handling.

Root Cause

The root cause is improper neutralization of user-supplied input during web page generation [CWE-79]. The Session Recording interface accepts input that contains HTML or JavaScript control characters and outputs them to administrative or operator views without contextual encoding. Combined with improper control of dynamically managed code resources [CWE-913], the component lacks defense-in-depth controls such as a strict Content Security Policy.

Attack Vector

Exploitation requires network access to the Session Recording management interface and authenticated high-privileged access. An attacker injects a script payload into a field or parameter processed by the Session Recording server. The payload is rendered when an administrator or operator views the affected page, leading to script execution in their browser. From there, the attacker can steal session tokens, perform actions on behalf of the victim, or pivot deeper into the Citrix management plane.

No public proof-of-concept code has been published for this vulnerability. Refer to the Citrix Security Bulletin for CVE-2023-6184 for vendor-supplied technical context.

Detection Methods for CVE-2023-6184

Indicators of Compromise

Unexpected <script> tags, JavaScript event handlers, or HTML entities appearing in Session Recording metadata fields, comments, or audit records.
Outbound HTTP requests from administrator browsers to unfamiliar domains immediately after loading Session Recording management pages.
New or modified administrator accounts created shortly after a privileged user accessed the Session Recording console.
Anomalous authentication events using Session Recording service accounts outside their normal operating windows.

Detection Strategies

Inspect Session Recording IIS and application logs for request parameters containing script tags, encoded HTML payloads, or unusual URL-encoded JavaScript sequences.
Monitor browser-side telemetry on administrator workstations for script execution originating from Session Recording domains.
Correlate privileged session activity with subsequent suspicious administrative actions in the Citrix environment.

Monitoring Recommendations

Enable verbose logging on the Session Recording server and forward logs to a centralized analytics platform for retention and correlation.
Alert on access to Session Recording administrative endpoints from non-administrative source networks or unmanaged endpoints.
Track changes to Session Recording policies and configuration objects, since XSS-driven session hijacking can be used to alter recording scope.

How to Mitigate CVE-2023-6184

Immediate Actions Required

Apply the fixed Session Recording builds referenced in the Citrix security bulletin for all 1912 LTSR and 2203 LTSR deployments.
Restrict access to the Session Recording management interface to a dedicated administrative network segment.
Require multi-factor authentication for all Citrix administrative accounts that interact with Session Recording.
Audit existing Session Recording administrator accounts and remove any unnecessary high-privileged access.

Patch Information

Citrix has published remediation guidance and fixed builds in the Citrix Security Bulletin for CVE-2023-6184. Customers running Citrix Virtual Apps and Desktops 1912 LTSR or 2203 LTSR with the Session Recording component installed must upgrade to the vendor-specified Session Recording version that contains the fix. The patch addresses both the input neutralization defect and the related dynamic code resource handling issues.

Workarounds

Limit Session Recording console access to a hardened jump host used exclusively for Citrix administration.
Enforce browser-level protections such as strict same-site cookies and modern browser versions on administrator workstations.
Reduce the number of high-privileged accounts that can author Session Recording policies, since exploitation requires high privileges per the CVSS vector.

bash

# Configuration example: restrict Session Recording management endpoint to admin subnet via Windows Firewall
New-NetFirewallRule -DisplayName "Restrict Citrix Session Recording Admin" `
  -Direction Inbound `
  -Protocol TCP `
  -LocalPort 443 `
  -RemoteAddress 10.10.20.0/24 `
  -Action Allow