What is CVE-2025-13821?

CVE-2025-13821 is a medium-severity vulnerability in Mattermost, classified under Information Disclosure. CVSS score: 5.7/10. Published 2026-02-16.

How severe is CVE-2025-13821?

Medium severity. CVSS v3 base score is 5.7 out of 10.

Information disclosure in Mattermost

CVE-2025-13821

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to sanitize sensitive data in WebSocket messages which allows authenticated users to exfiltrate password hashes and MFA secrets via profile nickname updates or email verification events. Mattermost Advisory ID: MMSA-2025-00560

Vulnerability class: Information Disclosure

Published 2026-02-16 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.002 (9.5th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 9th percentile — 9.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Mattermost — versions 11.1.0, 10.11.0, 11.2.0
Mattermost Server

Weakness classification (CWE)

CWE-200 — Information Disclosure

References

mattermost.com/security-updates (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2025-13821?: CVE-2025-13821 is a medium-severity vulnerability in Mattermost, classified under Information Disclosure. CVSS score: 5.7/10. Published 2026-02-16.
How severe is CVE-2025-13821?: Medium severity. CVSS v3 base score is 5.7 out of 10.