What is CVE-2026-3473?

CVE-2026-3473 is a medium-severity vulnerability in Mattermost, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 5.9/10. Published 2026-05-22.

How severe is CVE-2026-3473?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Auth bypass in Mattermost

CVE-2026-3473

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or t…

Vulnerability class: IDOR (Insecure Direct Object Reference)

EPSS: 0.000 (10.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N.

Affected products

Mattermost — versions 11.6.0, 11.5.0, 11.4.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-639 — Authorization Bypass Through User-Controlled Key

References

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

Frequently asked questions

What is CVE-2026-3473?: CVE-2026-3473 is a medium-severity vulnerability in Mattermost, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 5.9/10. Published 2026-05-22.
How severe is CVE-2026-3473?: Medium severity. CVSS v3 base score is 5.9 out of 10.