CVE-2026-20796 — Time-of-check time-of-use vulnerability in common teams API

CVE-2026-20796

Time-of-check time-of-use vulnerability in common teams API PUBLISHED

Description (CNA)

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 API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

Affected (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 10.11.0 through 10.11.9; unaffected 11.3.0; unaffected 10.11.10

CWE

CWE-367

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.