# CVE-2026-39878: Chamilo LMS stored XSS in user registration form

Source: https://junglewise.ai/threats/cve-2026-39878-chamilo-lms-stored-xss-in-user-registration-form  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-20. Updated: 2026-07-20  
License: CC BY 4.0 with a link back

CVE-2026-39878 · Severity: critical · CVSS 9.3 · Published 2026-07-20

Chamilo LMS, a popular learning management system, contains a security flaw in its user registration form. An unauthorized attacker can submit a malicious registration that, when viewed by a system administrator, allows the attacker to take over the administrator's account. This grants the attacker full control over the platform, including access to all student data, grades, and course content.

## Quick answers

**Is CVE-2026-39878 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39878 being exploited in the wild.

**How severe is CVE-2026-39878?** Critical severity, with a CVSS score of 9.3, published 20 July 2026.

**Which products and versions are affected?** Chamilo Chamilo LMS <= 1.11.38.

**Is there a fix for CVE-2026-39878?** A patch was published on 2026-07-20: Patch confirmed available in version 1.11.40 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-39878 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-39878?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stored Cross-Site Scripting (XSS) vulnerability exists in Chamilo LMS versions <= 1.11.38 due to improper input sanitization in the user registration form (main/auth/inscription.php) and insufficient output encoding in the administrative user list (main/admin/user_list.php). The vulnerability stems from a bypass of the Security::remove_XSS() function using null byte insertion and the failure to use htmlspecialchars() with ENT_QUOTES when rendering user names in HTML 'alt' and 'title' attributes. An unauthenticated attacker can inject malicious JavaScript that executes when an administrator views the user list. This leads to a session takeover and full administrative access to the LMS platform. The issue is resolved in version 1.11.40.

## Affected products

- Chamilo Chamilo LMS <= 1.11.38

## Timeline

- 2026-07-07: advisory: GitHub Security Advisory published
- 2026-07-20: disclosed: CVE published to NVD
- 2026-07-20: patched: Patch confirmed available in version 1.11.40

## References

- [https://github.com/chamilo/chamilo-lms/security/advisories/GHSA-gcjp-f7jm-rrrg](https://github.com/chamilo/chamilo-lms/security/advisories/GHSA-gcjp-f7jm-rrrg)