CVE-2026-4054CWE-754

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

Medium · published May 15, 2026

CVSS v3.1
4.3
EPSS
0%
Percentile
35.5
In the wild
Unconfirmed
What it is

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

The record
Technical detail
CVSS v3.1
4.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
CVSS v4.0
Not supplied
EPSS
0.00423 · 35.5th percentile
Weakness
CWE-754 · Improper Check for Unusual or Exceptional Conditions
Published
2026-05-15T18:32Z
EPSS history
Timeline
  • 15 MAY 18:32Z
    SVG content served through Mattermost image proxy despite Content-Type restrictions causes client-side denial of service
    cvelistv5