Executive Summary

CVE-2026-30876 is a user enumeration vulnerability in Chamilo LMS versions up to 1.11.34. The vulnerability occurs because the system responds differently to requests with valid usernames compared to invalid ones. This difference in responses allows an attacker to determine whether a specific username exists in the system without authorization.

This issue is classified under CWE-204 (Observable Response Discrepancy) and was fixed in version 1.11.36 of Chamilo LMS.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability allows an attacker to enumerate valid usernames in the Chamilo LMS system by observing differences in system responses. Knowing valid usernames can facilitate further attacks such as targeted phishing, brute force password attempts, or social engineering.

Useful 0 Not Useful 0

Compliance Impact

I don't know

Useful 0 Not Useful 0

Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by observing the responses from the Chamilo LMS application when submitting requests with different usernames. Specifically, sending requests with valid and invalid usernames and comparing the responses can reveal distinguishable differences that indicate user enumeration.'}, {'type': 'paragraph', 'content': 'For example, you can use command-line tools like curl to send HTTP requests with different usernames and analyze the responses for discrepancies.'}, {'type': 'list_item', 'content': 'curl -i -X POST -d "username=valid_username" https://your-chamilo-instance/login'}, {'type': 'list_item', 'content': 'curl -i -X POST -d "username=invalid_username" https://your-chamilo-instance/login'}, {'type': 'paragraph', 'content': 'By comparing the HTTP status codes, response bodies, or response times between these requests, you can detect if the application is leaking information about the validity of usernames.'}] [1]

Useful 0 Not Useful 0

Mitigation Strategies

The immediate step to mitigate this vulnerability is to upgrade Chamilo LMS to version 1.11.36 or later, where the issue has been patched.

Until the upgrade can be performed, consider implementing generic error messages that do not reveal whether a username is valid or invalid, to reduce the risk of user enumeration.

Useful 0 Not Useful 0