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 credentials via the plaintext values present in the exported plugin configuration.. Mattermost Advisory ID: MMSA-2026-00605

Vulnerability class: Information Disclosure

Published · last modified .

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.

EPSS exploit prediction

EPSS: 0.004 (34.3th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 34.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-6347: held from 0.003 to 0.004.

EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.002

Affected products

Weakness classification (CWE)

References

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.