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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

PUBLISHED Reserved 2026-03-12 | Published 2026-05-15 | Updated 2026-05-15 | Assigner Mattermost




MEDIUM: 4.3CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Problem types

CWE-754: Improper Check for Unusual or Exceptional Conditions

Product status

Default status
unaffected

11.5.0 (semver)
affected

10.11.0 (semver)
affected

11.4.0 (semver)
affected

11.6.0
unaffected

11.5.2
unaffected

10.11.14
unaffected

11.4.4
unaffected

Credits

mk7120 finder

References

mattermost.com/security-updates (MMSA-2026-00630) vendor-advisory

cve.org (CVE-2026-4054)

nvd.nist.gov (CVE-2026-4054)

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