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

Published 2026-03-16 · last modified 2026-06-17.

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.

EPSS exploit prediction

EPSS: 0.003 (15.4th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.4% 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 10.11.0, 11.4.0, 10.11.11
Mattermost Server

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

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

Frequently asked questions

What is CVE-2026-26230?: 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.