CVE-2021-36403 Moodle has a Hidden Functionality vulnerability

What is CVE-2021-36403?

CVE-2021-36403 is a medium-severity cross-site scripting vulnerability in Moodle Moodle, published on 6 Mar 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In Moodle, in some circumstances, email notifications of messages could have the link back to the original message hidden by HTML, which may pose a phishing risk.

Weakness: CWE-912

Which versions are affected by CVE-2021-36403?

7 open source packages ship an affected version, including moodle/moodle and moodle. It affects 1 product.

Products include Moodle Moodle.

How do I fix CVE-2021-36403?

Upgrade moodle/moodle to a fixed version for your release line: 3.9.8, 3.10.5 or 3.11.1.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2021-36403 being exploited?

There is no known exploitation of CVE-2021-36403 in the wild and no public exploit code.

Other vulnerabilities in Moodle Moodle

• CVE-2006-4935 File upload in n/a Critical 10.0
• CVE-2006-4936 Moodle does not properly validate module instance id Critical 10.0
• CVE-2004-2233 Unknown "front page vulnerability with Moodle servers" for Moodle before 1.3.2 has unknown impact and attack vectors. Critical 10.0
• CVE-2004-2235 Cross-site scripting in n/a Critical 10.0
• CVE-2004-2236 Other in n/a Critical 10.0

All Moodle Moodle vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-moodle-2021-36403, GHSA-j9cw-5cpj-9qj5, UBUNTU-CVE-2021-36403.