What is CVE-2026-6341?

CVE-2026-6341 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-05-18.

How severe is CVE-2026-6341?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Auth bypass in Mattermost

CVE-2026-6341

Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to have API-level checks on which groups the user can create issues or attach comments to which allows a user that is member of multiple groups to create issues to a locked group via direct API requests. Mattermost Advisory ID: MMSA-2026-00602

Vulnerability class: Broken Access Control

Published 2026-05-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (15.3th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.3% 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: 0.003 · change: +0.001

Affected products

Mattermost — versions 0, 11.6.0, 11.5.2
Mattermost Server

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

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

Frequently asked questions

What is CVE-2026-6341?: CVE-2026-6341 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-05-18.
How severe is CVE-2026-6341?: Medium severity. CVSS v3 base score is 4.3 out of 10.