CVE-2026-6339

4.3 MEDIUM
Published: May 18, 2026 Modified: May 18, 2026
View on NVD

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

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://mattermost.com/security-updates
Source: responsibledisclosure@mattermost.com
Vendor Advisory

1 reference(s) from NVD

Quick Stats

CVSS v3 Score
4.3 / 10.0
EPSS (Exploit Probability)
0.1%
2th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

mattermost