Vulnerability · Published Mar 18, 2026 · Assigned by GitHub_M

CVE-2026-30884mdjnelson/moodle-mod_customcert Vulnerable to Authorization Bypass Through User-Controlled Key

Critical 9.6

In plain English

A critical-severity authorization bypass via user-controlled key in moodle-mod_customcert from mdjnelson. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities).

Severity (CVSS 3.1)9.6Critical

Exploit odds (30 days)0.2%top 93.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

mdjnelson/moodle-mod_customcert is a Moodle plugin for creating dynamically generated certificates with complete customization via the web browser. Prior to versions 4.4.9 and 5.0.3, a teacher who holds `mod/customcert:manage` in any single course can read and silently overwrite certificate elements belonging to any other course in the Moodle installation. The `core_get_fragment` callback `editelement` and the `mod_customcert_save_element` web service both fail to verify that the supplied `elementid` belongs to the authorized context, enabling cross-course information disclosure and data tampering. Versions 4.4.9 and 5.0.3 fix the issue.

Affected products (as reported)

Vendor	Product	Versions
mdjnelson	moodle-mod_customcert	< 4.4.9>= 5.0.0, < 5.0.3

Weakness: CWE-639 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

References

https://github.com/mdjnelson/moodle-mod_customcert/security/advisories/GHSA-8pjr-j7r4-ccjx x_refsource_CONFIRM
https://github.com/mdjnelson/moodle-mod_customcert/commit/a1494a80fb953f187f7888a7394cbf9d13c28468 x_refsource_MISC
https://github.com/mdjnelson/moodle-mod_customcert/commit/ddc8f01f1e19fb61202f6013a38ef757486d3ba0 x_refsource_MISC