Vulnerability · Published May 18, 2026 · Assigned by Mattermost

CVE-2026-6347Mattermost Calls plugin exposes TURN server credentials in plaintext in support packets

High 7.6

In plain English

A high-severity information exposure in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.6High

Exploit odds (30 days)0.3%top 81.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Go	github.com/mattermost/mattermost-plugin-calls	1.12.0-rc2	GHSA-82j6-4fq7-fx62
Go	github.com/mattermost/mattermost-plugin-calls	1.12.0-rc2	GO-2026-5238
Go	github.com/mattermost/mattermost-server	11.5.2	GHSA-82j6-4fq7-fx62
Go	github.com/mattermost/mattermost-server	10.11.14	GHSA-82j6-4fq7-fx62
Go	github.com/mattermost/mattermost-server	11.4.4	GHSA-82j6-4fq7-fx62
Go	github.com/mattermost/mattermost-server	10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible	GO-2026-5238

Affected products (as reported)

Vendor	Product	Versions
Mattermost	Mattermost	11.5.0 – through 11.5.110.11.0 – through 10.11.1311.4.0 – through 11.4.3

Weakness: CWE-200 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:L

References

MMSA-2026-00605 vendor-advisory