What is CVE-2026-6739?

CVE-2026-6739 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 6.7/10. Published 2026-06-12.

How severe is CVE-2026-6739?

Medium severity. CVSS v3 base score is 6.7 out of 10.

Auth bypass in Mattermost

CVE-2026-6739

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to require system-level permission when patching protected default system roles, which allows authenticated users with delegated user-man…

Vulnerability class: Broken Access Control

EPSS: 0.003 (17.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L.

Affected products

Mattermost — versions 11.6.0, 11.5.0, 10.11.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

responsibledisclosure@mattermost.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-6739?: CVE-2026-6739 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 6.7/10. Published 2026-06-12.
How severe is CVE-2026-6739?: Medium severity. CVSS v3 base score is 6.7 out of 10.