CVE-2026-21386 — Private channel enumeration via /mute slash command
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 …
Published: 2026-03-16 · CVSS: 4.3 · CVSS 3.1
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
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7