What is CVE-2026-16047?

CVE-2026-16047 is a medium-severity vulnerability in Mattermost, classified under Missing Authorization. CVSS score: 4.3/10. Published 2026-08-17.

How severe is CVE-2026-16047?

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

Auth bypass in Mattermost

CVE-2026-16047

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674

Vulnerability class: Broken Access Control

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:L/I:N/A:N.

Affected products

Mattermost — versions 11.7.0, 10.11.0, 11.8.0

Weakness classification (CWE)

CWE-862 — Missing Authorization

References

responsibledisclosure@mattermost.com (vendor-advisory)

Frequently asked questions

What is CVE-2026-16047?: CVE-2026-16047 is a medium-severity vulnerability in Mattermost, classified under Missing Authorization. CVSS score: 4.3/10. Published 2026-08-17.
How severe is CVE-2026-16047?: Medium severity. CVSS v3 base score is 4.3 out of 10.