What is CVE-2026-26230?

CVE-2026-26230 is a low-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 3.8/10. Published 2026-03-16.

How severe is CVE-2026-26230?

Low severity. CVSS v3 base score is 3.8 out of 10.

Auth bypass in Mattermost

CVE-2026-26230

Mattermost versions 10.11.x <= 10.11.10 fail to properly validate permission requirements in the team member roles API endpoint which allows team administrators to demote members to guest role. Mattermost Advisory ID: MMSA-2025-00531

Vulnerability class: Broken Access Control

EPSS: 0.000 (11.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 3.8 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N.

Affected products

Mattermost — versions 10.11.0, 11.4.0, 10.11.11

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

MMSA-2025-00531 (vendor-advisory)

Frequently asked questions

What is CVE-2026-26230?: CVE-2026-26230 is a low-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 3.8/10. Published 2026-03-16.
How severe is CVE-2026-26230?: Low severity. CVSS v3 base score is 3.8 out of 10.