CVE-2026-6339

MediumCVSS 4.3/10Last modified Oct 14, 2026

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

Metrics

CVSS 3.1 4.3/10CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Weakness enumeration

CWE-346

Affected software

No affected versions have been published.

Timeline

Published: May 18, 2026
Last modified: Oct 14, 2026
NVD status: Analyzed

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