VULNERABILITY INTELLIGENCE

CVE-2026-21386

CVSS score4.3 MEDIUM
EPSS probability0.19%
CISA KEVNot currently listed
Published2026-03-16
Last modified2026-06-17
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Description

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to use consistent error responses when handling the /mute command which allows an authenticated team member to enumerate private channels they are not authorized to know about via differing error messages for nonexistent versus private channels. Mattermost Advisory ID: MMSA-2026-00588

Weakness classification

  • responsibledisclosure@mattermost.com: CWE-203

Primary references