CVE-2026-4054
Medium
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
SeverityMedium
CVSS4.3
Exploit probability—
Product
Mattermost Server
PublishedMay 15, 2026
First seenMay 15, 2026
Weakness typeCWE-754CWE-754
How to fix
Update
- mattermost mattermost_server10.11.14, 11.4.4, 11.5.2 or later
- github.com/mattermost/mattermost-server11.5.2, 0.0.0-20260414103857-b21ef302025e, 11.4.4, 11.4.4+incompatible, 11.5.2+incompatible or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.14, 11.4.0 ≤ v < 11.4.4, 11.5.0 ≤ v < 11.5.2 | 10.11.14, 11.4.4, 11.5.2 |
| github.com/mattermost/mattermost-serverGo | 11.5.0 ≤ v < 11.5.2, 0.0.0-20250731163400-5b955468ea1e ≤ v < 0.0.0-20260414103857-b21ef302025e, 11.4.0 ≤ v < 11.4.4, 11.4.0+incompatible ≤ v < 11.4.4+incompatible, 11.5.0+incompatible ≤ v < 11.5.2+incompatible | 11.5.2, 0.0.0-20260414103857-b21ef302025e, 11.4.4, 11.4.4+incompatible, 11.5.2+incompatible |
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