What is CVE-2026-20796?

CVE-2026-20796 is a low-severity vulnerability in Mattermost, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 3.1/10. Published 2026-02-13.

How severe is CVE-2026-20796?

Low severity. CVSS v3 base score is 3.1 out of 10.

Vulnerability in Mattermost

CVE-2026-20796

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams…

Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)

EPSS: 0.002 (9.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

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

Affected products

Mattermost — versions 10.11.0, 11.3.0, 10.11.10
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-367 — Time-of-check Time-of-use (TOCTOU) Race Condition

References

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

Frequently asked questions

What is CVE-2026-20796?: CVE-2026-20796 is a low-severity vulnerability in Mattermost, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 3.1/10. Published 2026-02-13.
How severe is CVE-2026-20796?: Low severity. CVSS v3 base score is 3.1 out of 10.