What is CVE-2026-16044?

CVE-2026-16044 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-08-17.

How severe is CVE-2026-16044?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Auth bypass in Mattermost

CVE-2026-16044

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID: MMSA-2026-00672

Vulnerability class: Broken Access Control

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L.

Affected products

Mattermost — versions 11.7.0, 10.11.0, 11.9.0

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

responsibledisclosure@mattermost.com (vendor-advisory)

Frequently asked questions

What is CVE-2026-16044?: CVE-2026-16044 is a medium-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-08-17.
How severe is CVE-2026-16044?: Medium severity. CVSS v3 base score is 5.4 out of 10.