CVE-2026-4054 MEDIUM

CVE-2026-4054: SVG content served through Mattermost image proxy despite Content-Type restrictions causes client-side denial of service

Vendor Mattermost
Product Mattermost
Weakness CWE-754
Published May 15, 2026
Last update May 15, 2026
View on NVD All CVEs

CVSS base score

4.3/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction Required
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

What the vulnerability does

01Description

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 origin under a non-SVG Content-Type header (e.g. image/png) embedded in an og:image meta tag or Markdown image link.. Mattermost Advisory ID: MMSA-2026-00630

Key dates

02Disclosure timeline

May 15, 2026 CVE published
May 15, 2026 Record updated