Attack Chain

1. The attacker identifies a valid email address associated with a Chamilo LMS user. This information may be obtained through OSINT or data breaches.
2. The attacker navigates to the password reset page of the Chamilo LMS instance.
3. The attacker enters the victim’s email address into the password reset form.
4. The system generates a password reset token by applying SHA1 to the victim’s email address without any salt or random component.
5. The attacker computes the SHA1 hash of the victim’s email address offline.
6. The attacker uses the computed SHA1 hash as the password reset token in a crafted request to the password reset confirmation endpoint.
7. The Chamilo LMS instance validates the attacker-supplied token against the SHA1 hash of the email.
8. The attacker sets a new password for the victim’s account and gains full access to the compromised account.

Impact

Successful exploitation of CVE-2026-33707 allows an attacker to take complete control of user accounts within the Chamilo LMS platform. This can lead to data breaches, modification of course content, disruption of educational activities, and potential reputational damage for the affected institution. The lack of rate limiting on password reset requests can allow for automated account takeover attempts affecting many users. Given the widespread use of Chamilo LMS in educational institutions and organizations globally, the potential impact is significant.

Recommendation

• Immediately upgrade Chamilo LMS installations to version 1.11.38 or 2.0.0-RC.3 to remediate CVE-2026-33707.
• Implement rate limiting on password reset requests to mitigate automated attacks attempting to exploit this vulnerability (reference: Overview section).
• Deploy the Sigma rules below to detect attempts to exploit this vulnerability by monitoring password reset requests (reference: rules section).
• Monitor web server logs for suspicious password reset requests originating from unusual IPs or with unusually high frequency (reference: rules logsource).