What is GHSA-xvcx-mgpc-5xh3?

GHSA-xvcx-mgpc-5xh3 is a security advisory published by GitHub Security Advisories with Medium severity. Mattermost versions 11.5.x \u003c= 11.5.1, 11.4.x \u003c= 11.4.3 fail to validate the X-Requested-With...

Which CVE IDs does GHSA-xvcx-mgpc-5xh3 cover?

GHSA-xvcx-mgpc-5xh3 covers the following CVE IDs: CVE-2026-6339. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

What is the CVSS v3 score of GHSA-xvcx-mgpc-5xh3?

GHSA-xvcx-mgpc-5xh3 has a CVSS v3 base score of 4.3, published by GitHub Security Advisories.

GHSA-xvcx-mgpc-5xh3MediumCVSS 4.3

Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With...

Vendor

GitHub Security Advisories

Published

May 18, 2026

Last Modified

May 18, 2026

🔗 CVE IDs covered (1)

CVE-2026-6339 →

📋 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

🔗 References (3)

https://nvd.nist.gov/vuln/detail/CVE-2026-6339
https://mattermost.com/security-updates
https://github.com/advisories/GHSA-xvcx-mgpc-5xh3