CVE-2026-4054 Details
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
A denial-of-service vulnerability has been identified in Mattermost versions 11.5.x through 11.5.1, 10.11.x through 10.11.13, and 11.4.x through 11.4.3. The issue arises because these versions fail to properly validate the response body of proxied images. This flaw allows remote attackers to cause client-side denial-of-service by embedding an SVG file, served from an attacker-controlled origin under a non-SVG Content-Type header (such as image/png), into an og:image meta tag or a Markdown image link.
Users can upgrade to Mattermost versions 11.7.0, 11.6.1, or 11.4.5 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 15, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://mattermost.com/security-updates | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-754 | Improper Check for Unusual or Exceptional Conditions | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mattermost mattermost server | >= 10.11.0, < 10.11.14 >= 11.4.0, < 11.4.4 >= 11.5.0, < 11.5.2 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 18, 2026 | Initial Analysis | [email protected] |
| May 15, 2026 | New CVE Received | [email protected] |