What is CVE-2026-4054?

CVE-2026-4054 is a medium-severity vulnerability in Mattermost, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 4.3/10. Published 2026-05-15.

How severe is CVE-2026-4054?

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

Vulnerability in Mattermost

CVE-2026-4054

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to validate the response body of proxied images, which allows a remote attacker to enact client-side DoS via an SVG file served from an attacker-controlled or…

EPSS: 0.001 (26.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L.

Affected products

Mattermost — versions 11.5.0, 10.11.0, 11.4.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-754 — Improper Check for Unusual or Exceptional Conditions

References

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

Frequently asked questions

What is CVE-2026-4054?: CVE-2026-4054 is a medium-severity vulnerability in Mattermost, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 4.3/10. Published 2026-05-15.
How severe is CVE-2026-4054?: Medium severity. CVSS v3 base score is 4.3 out of 10.