CVE-2026-4054

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

State: Published
Severity: 4.3 Medium
Published: May 15, 2026
Updated: May 15, 2026
Reserved: Mar 12, 2026

Read the record on cve.org

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

Scores

CVSS	Score	Vector	Source
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L	Mattermost

Weaknesses

CWE-754 Improper Check for Unusual or Exceptional Conditions

Affected Products

Product	Versions
MattermostMattermost	11.5.0 through 11.5.1Affected 10.11.0 through 10.11.13Affected 11.4.0 through 11.4.3Affected 11.6.0Not affected 11.5.2Not affected 10.11.14Not affected 11.4.4Not affected

References

MMSA-2026-00630vendor-advisory

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.