CVE-2026-4054 — SVG content served through Mattermost image proxy despite Content-Type restrictions causes client-side denial of service
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-…
Published: 2026-05-15 · CVSS: 4.3 · CVSS 3.1
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
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7