CVE-2021-47857

HIGH

Moodle 3.10.3 - Stored Cross-Site Scripting in Calendar Event Subtitle Field

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2021-47857. PoCs published by Vincent666.

AI-analyzed exploit summary This exploit demonstrates a persistent XSS vulnerability in Moodle 3.10.3 via the 'label' field in the calendar event creation form. The payload is injected into the subtitle track URL label, which is then rendered when the event is viewed.

Description

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 track label to execute arbitrary code when users view the event.

Exploits (1)

exploitdb WORKING POC
by Vincent666 · textwebappsphp
https://www.exploit-db.com/exploits/49714

This exploit demonstrates a persistent XSS vulnerability in Moodle 3.10.3 via the 'label' field in the calendar event creation form. The payload is injected into the subtitle track URL label, which is then rendered when the event is viewed.

Classification
Working Poc 90%
Attack Type
Xss
Complexity
Trivial
Reliability
Reliable
Target: Moodle 3.10.3
Auth required
Prerequisites: Authenticated user access to Moodle · Ability to create calendar events
MITRE ATT&CK
devstral-2 · analyzed Feb 16, 2026 Full analysis →

References (3)

Core 3
Core References
Exploit, Third Party Advisory exploit
https://www.exploit-db.com/exploits/49714
Various Sources product
https://moodle.org/

Scores

CVSS v3 7.2
EPSS 0.0031
EPSS Percentile 22.5%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact partial

Details

CWE
CWE-79
Status published
Products (1)
moodle/moodle 3.10.3
Published Jan 21, 2026
Tracked Since Feb 18, 2026