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CVE-2026-6339

4.3 medium SSVC exploitation: none Analyzed
NVD · CVE.org

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

Fix

Patch, vendor advisory and mitigation references on NVD 1

Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.

Change history 1

  1. First seenCVSS 4.3 · mattermostNVD modified 2026-10-14 20:10

Affected (CPE criteria) 1

  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

References 1