PT-2026-3809 · Moodle+1 · Moodle+1

Published 2021-03-25 · Updated 2026-03-06 · CVE-2021-47857

Positive Technologies (AI Summary)

CVSS v3.1

7.2

High

Base vector

AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Name of the Vulnerable Software and Affected Versions Moodle versions prior to 3.10.4

Description A security issue exists in Moodle related to insufficient protection of the web page structure within the calendar event subtitle field. Successful exploitation of this issue could allow a remote attacker to conduct cross-site scripting (XSS) attacks. Specifically, an attacker can create a calendar event with malicious JavaScript code embedded in the subtitle track label. When users view the event, this malicious code will execute, potentially allowing the attacker to execute arbitrary code.

Recommendations Update to Moodle version 3.10.4 or later.

Exploit

Fix

XSS

Weakness Enumeration

CWE-79

Related Identifiers

BDU:2026-00978

BIT-MOODLE-2021-47857

CVE-2021-47857

Affected Products

Moodle

Red Os

References · 9

• 🔥 https://exploit-db.com/exploits/49714 · Exploit
• https://bdu.fstec.ru/vul/2026-00978 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2021-47857 · Security Note
• https://osv.dev/vulnerability/BIT-moodle-2021-47857 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2021-47857 · Vendor Advisory
• https://redos.red-soft.ru/support/secure/uyazvimosti/support/secure/uyazvimosti/uyazvimost-moodle-cve-2021-47857-7.3 · Note
• https://github.com/advisories/GHSA-px56-6vfj-h8xp?ysclid=mkxug07x1872998433 · Note
• https://moodle.org · Note
• https://vulncheck.com/advisories/moodle-label-persistent-cross-site-scripting · Note