CVE-2026-6339

4.3 MEDIUM

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 w...

Published: 2026-05-18 · Last updated: 2026-05-18

Severity and scoring

CVSS: 4.3 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CWE: CWE-346

Affected products

Vendor	Product
mattermost	mattermost_server

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

Source: NVD

References

[NVD]https://nvd.nist.gov/vuln/detail/CVE-2026-6339
[Vendor advisory]https://mattermost.com/security-updates

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