What is CVE-2026-6347?

CVE-2026-6347 is a high-severity vulnerability in Mattermost, classified under Information Disclosure. CVSS score: 7.6/10. Published 2026-05-18.

How severe is CVE-2026-6347?

High severity. CVSS v3 base score is 7.6 out of 10.

Information disclosure in Mattermost

CVE-2026-6347

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to sanitize sensitive configuration fields in the Mattermost Calls plugin which allows an attacker with access to a support packet to obtain TURN server crede…

Vulnerability class: Information Disclosure

EPSS: 0.001 (16.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:L.

Affected products

Mattermost — versions 11.5.0, 10.11.0, 11.4.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-200 — Information Disclosure

References

responsibledisclosure@mattermost.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-6347?: CVE-2026-6347 is a high-severity vulnerability in Mattermost, classified under Information Disclosure. CVSS score: 7.6/10. Published 2026-05-18.
How severe is CVE-2026-6347?: High severity. CVSS v3 base score is 7.6 out of 10.