CVE-2021-43558

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-11-22 · updated 2026-06-17
Weakness: CWE-79

Description

A flaw was found in Moodle in versions 3.11 to 3.11.3, 3.10 to 3.10.7, 3.9 to 3.9.10 and earlier unsupported versions. A URL parameter in the filetype site administrator tool required extra sanitizing to prevent a reflected XSS risk.

Affected products

Fedoraproject Extra Packages For Enterprise Linux: 7.0
Fedoraproject Fedora: 35
Moodle: through 3.8.8; from 3.9.0 before 3.9.11; from 3.10.0 before 3.10.8; from 3.11.0 before 3.11.4 — fixed in 3.10.8, 3.11.4, 3.9.11

How to fix

Upgrade to a fixed version: Moodle 3.10.8, 3.11.4, 3.9.11. Check the vendor advisory for mitigations.

References

https://bugzilla.redhat.com/show_bug.cgi?id=2021515
https://moodle.org/mod/forum/discuss.php?d=429097
https://bugzilla.redhat.com/show_bug.cgi?id=2021515
https://moodle.org/mod/forum/discuss.php?d=429097

Get alerted when CVE-2021-43558 or the next vulnerability affects your stack