CVE-2025-53021: moodle Session Fixation (CVSS 4.2)

Description

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.

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CVSS v3.1 Score

4.2

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

Weakness Type (CWE)

CWE-384 CWE-384

Affected Products

Vendor	Product	Versions
moodle	moodle	3.0.0 — 3.11.18

References

Other References

https://github.com/moodle/moodle/releases/tag/v3.11.18 https://moodledev.io/general/releases#moodle-311 https://rentry.co/moodle-oauth2-cve

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 4.2 (MEDIUM).

How severe is CVE-2025-53021? +

CVE-2025-53021 has a CVSS v3.1 score of 4.2 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-53021? +

CVE-2025-53021 affects products from moodle, specifically: moodle. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-53021? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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