CVE-2024-40748 Overview
CVE-2024-40748 is a Cross-Site Scripting (XSS) vulnerability in Joomla! caused by a lack of output escaping in the id attribute of menu lists. The flaw is classified under CWE-79 and affects the Joomla! Content Management System (CMS) core. An unauthenticated attacker can inject script content through unsanitized menu list id attributes, leading to script execution in the context of users viewing affected pages. Joomla! published the issue in the Joomla Security Advisory.
Critical Impact
Attackers can inject arbitrary script content via menu list id attributes, enabling session theft, account takeover, and content manipulation against Joomla! users.
Affected Products
- Joomla! CMS core (see vendor advisory for affected version ranges)
- Joomla! Extended Long Term Support (ELTS) releases
- Sites rendering menu lists with unescaped id attribute values
Discovery Timeline
- 2025-01-07 - CVE-2024-40748 published to the National Vulnerability Database (NVD)
- 2025-06-04 - Last updated in the NVD database
Technical Details for CVE-2024-40748
Vulnerability Analysis
The vulnerability resides in Joomla!'s rendering of menu list HTML output. The id attribute value is emitted into the response without proper HTML attribute escaping. Attacker-controlled input that reaches this attribute can break out of the attribute context and inject script payloads. Because exploitation is network-based, requires no privileges, and needs no user interaction beyond visiting a page, the impact targets confidentiality of session data and stored content.
Root Cause
The root cause is missing output encoding in the templating path that constructs menu list elements. Values destined for the id attribute are not passed through Joomla!'s HTML attribute escaping helpers. This is a classic [CWE-79] failure where untrusted data is reflected into an HTML attribute without contextual escaping. See the Joomla Security Advisory for the affected code paths.
Attack Vector
An attacker crafts input that, when rendered as the id attribute of a menu list, contains attribute-breaking characters and JavaScript event handlers or <script> payloads. When a victim loads the affected page, the browser parses the injected markup and executes the payload in the site's origin. The result includes cookie theft, CSRF token exfiltration, and unauthorized actions performed as the victim. The Exploit Prediction Scoring System (EPSS) probability for this CVE is 0.404%.
No verified public proof-of-concept code is available. Refer to the vendor advisory for technical details on affected code paths and remediation specifics.
Detection Methods for CVE-2024-40748
Indicators of Compromise
- HTTP responses containing menu list elements where the id attribute includes characters such as ", ', <, >, or event handler substrings (onerror=, onload=, onclick=).
- Web server access logs showing requests with payload-like query parameters or path segments that map to menu item identifiers.
- Browser Content Security Policy (CSP) violation reports referencing inline script execution on Joomla! pages.
Detection Strategies
- Inspect rendered HTML for menu list nodes whose id attribute contains non-alphanumeric characters or quoted substrings.
- Deploy a Web Application Firewall (WAF) rule that flags requests targeting menu administration endpoints with HTML metacharacters.
- Correlate authentication anomalies, such as session reuse from new IP addresses, with prior visits to pages rendering attacker-influenced menu data.
Monitoring Recommendations
- Monitor administrative account logins and privilege changes following any visit to pages containing suspicious menu output.
- Log and alert on modifications to menu items, categories, and template overrides in the Joomla! administrator panel.
- Track outbound requests from end-user browsers to unknown domains shortly after Joomla! page loads, indicating possible script exfiltration.
How to Mitigate CVE-2024-40748
Immediate Actions Required
- Upgrade Joomla! to the fixed release identified in the Joomla Security Advisory.
- Audit existing menu items for attacker-controlled id values and remove or sanitize any suspicious entries.
- Rotate administrator credentials and invalidate active sessions on sites that may have served crafted menu output.
Patch Information
Joomla! addressed the missing output escaping in the menu list id attribute in the patched releases described in advisory 955-20250102. Administrators should apply the vendor update through the Joomla! Update component or by deploying the official package. Verify the upgrade by confirming the running version matches the fixed release listed in the advisory.
Workarounds
- Restrict access to the Joomla! administrator interface to trusted IP ranges until patching is complete.
- Enforce a strict Content Security Policy (CSP) that disallows inline scripts and limits script sources to known origins.
- Apply a WAF rule that blocks HTML metacharacters in parameters bound to menu item identifiers.
# Example CSP header to reduce XSS impact on Joomla! responses
Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self'
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
