VULNERABILITY INTELLIGENCE

CVE-2026-6339

CVSS score4.3 MEDIUM
EPSS probability0.11%
CISA KEVNot currently listed
Published2026-05-18
Last modified2026-10-14
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Description

Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost Advisory ID: MMSA-2026-00636

Weakness classification

  • CWE-346: Origin Validation Error

Primary references