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CVE PROGRAM SOURCE RECORD4.3 Medium

CVE-2026-4054

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

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Status
Published
Published
Updated
Assigning organization
Mattermost

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

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Mattermost Mattermost

Default version status: unaffected

  • 11.5.0 to ≤ 11.5.1affected
  • 10.11.0 to ≤ 10.11.13affected
  • 11.4.0 to ≤ 11.4.3affected
  • 11.6.0unaffected
  • 11.5.2unaffected
  • 10.11.14unaffected
  • 11.4.4unaffected

References