CVE-2026-0999 PUBLISHED

Authentication bypass via userID login when email and username login are disabled

Assigner: Mattermost
Reserved: 15.01.2026 Published: 16.02.2026 Updated: 16.02.2026

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
CVSS Score: 5.4

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

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.1.0 to 11.1.2 (incl.) affected from 10.11.0 to 10.11.9 (incl.) affected from 11.2.0 to 11.2.1 (incl.) Version 11.3.0 is unaffected Version 11.1.3 is unaffected Version 10.11.10 is unaffected Version 11.2.2 is unaffected

Solutions

Update Mattermost to versions 11.3.0, 11.1.3, 10.11.10, 11.2.2 or higher.

Credits

daw10 finder

References

MMSA-2025-00548

Problem Types

CWE-303: Incorrect Implementation of Authentication Algorithm CWE