CVE-2026-20796

LOW

Mattermost <10.11.9 - Info Disclosure

Title source: llm

Description

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

References (1)

[Various Sources] https://mattermost.com/security-updates

Scores

CVSS v3 3.1

EPSS 0.0001

EPSS Percentile 0.9%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

Classification

CWE

CWE-367

Status published

Affected Products (2)

mattermost/mattermost-server < 10.11.10Go

mattermost/mattermost_server < 10.11.10

Timeline

Published Feb 13, 2026

Tracked Since Feb 18, 2026