Vulnerability in Moodle
CVE-2025-53021
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.2 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (23.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 23rd percentile — 23.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000
Affected products
- Moodle — versions 3
Weakness classification (CWE)
References
- rentry.co/moodle-oauth2-cve (Third Party Advisory)
- github.com/moodle/moodle/releases/tag/v3.11.18 (Product)
- moodledev.io/general/releases (Product)
Frequently asked questions
- What is CVE-2025-53021?
- CVE-2025-53021 is a medium-severity vulnerability in Moodle, classified under Session Fixation. CVSS score: 4.2/10. Published 2025-06-24.
- How severe is CVE-2025-53021?
- Medium severity. CVSS v3 base score is 4.2 out of 10.