What is CVE-2026-4273?

CVE-2026-4273 is a low-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 3.7/10. Published 2026-05-18.

How severe is CVE-2026-4273?

Low severity. CVSS v3 base score is 3.7 out of 10.

Auth bypass in Mattermost

CVE-2026-4273

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation which allows an authenticated attacker to bypass token rota…

Vulnerability class: Broken Access Control

EPSS: 0.000 (10.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N.

Affected products

Mattermost — versions 11.5.0, 10.11.0, 11.6.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

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

Frequently asked questions

What is CVE-2026-4273?: CVE-2026-4273 is a low-severity vulnerability in Mattermost, classified under Incorrect Authorization. CVSS score: 3.7/10. Published 2026-05-18.
How severe is CVE-2026-4273?: Low severity. CVSS v3 base score is 3.7 out of 10.