| Package | Affected versions | Patched versions |
|---|---|---|
| github.com/mattermost/mattermost-server | ≥ 0.0.0-20250731163400-5b955468ea1e, < 0.0.0-20260414103857-b21ef302025e≥ 11.4.0, < 11.4.4≥ 11.4.0+incompatible, < 11.4.4+incompatible≥ 11.5.0, < 11.5.2≥ 11.5.0+incompatible, < 11.5.2+incompatible | 0.0.0-20260414103857-b21ef302025e11.4.411.4.4+incompatible11.5.211.5.2+incompatible |
| mattermost server | ≥ 10.11.0, < 10.11.14≥ 11.4.0, < 11.4.4≥ 11.5.0, < 11.5.2 | 10.11.1411.4.411.5.2 |
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.
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