CVE-2026-4054
SVG content served through Mattermost image proxy despite Content-Type restrictions causes client-side denial of service
CVSS Score
4.3
EPSS Score
0.0%
EPSS Percentile
0th
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
| CWE | CWE-754 |
| Vendor | mattermost |
| Product | mattermost |
| Published | May 15, 2026 |
| Last Updated | May 15, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low
Affected Versions
Mattermost / Mattermost
11.5.0 ≤ 11.5.1 10.11.0 ≤ 10.11.13 11.4.0 ≤ 11.4.3
Credits
mk7120