What is CVE-2021-47857?

CVE-2021-47857 is a high-severity vulnerability in Moodle, classified under Cross-site Scripting. CVSS score: 7.2/10. Published 2026-01-21.

How severe is CVE-2021-47857?

High severity. CVSS v3 base score is 7.2 out of 10.

XSS in Moodle

CVE-2021-47857

Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle t…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.001 (16.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N.

Affected products

Moodle — versions 3.10.3

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

ExploitDB-49714 (exploit)
Official Moodle Project Homepage (product)
VulnCheck Advisory: Moodle 3.10.3 - 'label' Persistent Cross Site Scripting (third-party-advisory)

Frequently asked questions

What is CVE-2021-47857?: CVE-2021-47857 is a high-severity vulnerability in Moodle, classified under Cross-site Scripting. CVSS score: 7.2/10. Published 2026-01-21.
How severe is CVE-2021-47857?: High severity. CVSS v3 base score is 7.2 out of 10.