CVE-2025-53021: Moodle

Medium severity, CVSS 4.2. EPSS: 0.3% chance of exploitation in the next 30 days.

A session fixation vulnerability in Moodle 3.x through 3.11.18 allows unauthenticated attackers to hijack user sessions via the sesskey parameter. The sesskey can be obtained without authentication and reused within the OAuth2 login flow, resulting in the victim's session being linked to the attacker's. Successful exploitation results in full account takeover. According to the Moodle Releases page, "Bug fixes for security issues in 3.11.x ended 11 December 2023." NOTE: This vulnerability only affects products that are no longer supported by the maintainer.

Affected products

• Moodle Moodle: from 3.0.0, up to and including 3.11.18

Published 2025-06-24. Last modified 2026-06-17.