CVE-2026-4054

MEDIUM

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

Title source: cna
STIX 2.1

Description

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

References (1)

Core 1
Core References
Vendor Advisory vendor-advisory
MMSA-2026-00630
https://mattermost.com/security-updates

Scores

CVSS v3 4.3
EPSS 0.0010
EPSS Percentile 26.6%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-754
Status published
Products (8)
Mattermost/Mattermost 10.11.0 - 10.11.13
Mattermost/Mattermost 10.11.14
Mattermost/Mattermost 11.4.0 - 11.4.3
Mattermost/Mattermost 11.4.4
Mattermost/Mattermost 11.5.0 - 11.5.1
Mattermost/Mattermost 11.5.2
Mattermost/Mattermost 11.6.0
mattermost/mattermost_server 10.11.0 - 10.11.14
Published May 15, 2026
Tracked Since May 16, 2026