What is CVE-2021-27131?

CVE-2021-27131 is a medium-severity vulnerability in Moodle, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2023-05-16.

How severe is CVE-2021-27131?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Moodle

CVE-2021-27131

Moodle 3.10.1 is vulnerable to persistent/stored cross-site scripting (XSS) due to the improper input sanitization on the "Additional HTML Section" via "Header and Footer" parameter in /admin/settings.php. This vulnerability is leading an attacker to steal admin and all user account cookies by storing the malicious XSS payload in Header and Footer. NOTE: this is disputed by the vendor because the "Additional HTML Section" for "Header and Footer" can only be supplied by an administrator, who is intentionally allowed to enter unsanitized input (e.g., site-specific JavaScript).

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.007 (48.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

Affected products

Moodle — versions 3.10.1
N/a — versions n/a

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

Frequently asked questions

What is CVE-2021-27131?: CVE-2021-27131 is a medium-severity vulnerability in Moodle, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2023-05-16.
How severe is CVE-2021-27131?: Medium severity. CVSS v3 base score is 5.4 out of 10.