CVE-2026-6339

CVSS Score & Metrics

Base Score

4.3 / 10

Vector String

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

Vulnerability 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

Vulnerability Details

Published Date

May 18, 2026

Last Modified

May 18, 2026

CWE ID

CWE-346

Source

NVD

Vendor

mattermost

Product

mattermost_server

External References

https://mattermost.com/security-updates

CVSS Score & Metrics

Vulnerability Description

Vulnerability Details

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