CVE-2026-2458 PUBLISHED

Unauthorized channel enumeration in private teams after member removal

Assigner: Mattermost
Reserved: 13.02.2026 Published: 16.03.2026 Updated: 16.03.2026

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate team membership when searching channels which allows a removed team member to enumerate all public channels within a private team via the channel search API endpoint.. Mattermost Advisory ID: MMSA-2025-00568

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CVSS Score: 4.3

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	Low
Privileges Required	Low	Integrity Impact	None
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.3.0 to 11.3.0 (incl.) affected from 11.2.0 to 11.2.2 (incl.) affected from 10.11.0 to 10.11.10 (incl.) Version 11.4.0 is unaffected Version 11.3.1 is unaffected Version 11.2.3 is unaffected Version 10.11.11 is unaffected

Solutions

Update Mattermost to versions 11.4.0, 11.3.1, 11.2.3, 10.11.11 or higher.

Credits

0x7oda7123 finder

References

MMSA-2025-00568

Problem Types

CWE-862: Missing Authorization CWE