#VU54987 Input validation error in Moodle - CVE-2021-36403

Vulnerability identifier: #VU54987

Vulnerability risk: Low

CVSSv4.0: 0.5 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-36403

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Moodle
Web applications / Other software

Vendor: moodle.org

Description

The vulnerability allows a remote attacker to perform phishing attack.

The vulnerability exists due to insufficient validation of user-supplied input when processing email notifications containing HTML. 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.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Moodle: 3.9.0 - 3.9.7, 3.10.0 - 3.11.0

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External links
https://moodle.org/mod/forum/discuss.php?d=424809
https://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-71919
https://tracker.moodle.org/browse/MDL-71919

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.