CVE-2026-21386CWE-203

Private channel enumeration via /mute slash command

Medium · published March 16, 2026

CVSS v3.1
4.3
EPSS
0%
Percentile
7.9
In the wild
Unconfirmed
What it is

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

The record
Technical detail
CVSS v3.1
4.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00187 · 7.9th percentile
Weakness
CWE-203 · Observable Discrepancy
Published
2026-03-16T14:51Z
EPSS history
Timeline
  • 16 MAR 14:51Z
    Private channel enumeration via /mute slash command
    cvelistv5