CVE-2026-0999

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

State: Published
Severity: 5.4 Medium
Published: Feb 16, 2026
Updated: Feb 17, 2026
Reserved: Jan 15, 2026

Description

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

Scores

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

Weaknesses

CWE-303 Incorrect Implementation of Authentication Algorithm

Affected Products

Product	Versions
MattermostMattermost	11.1.0 through 11.1.2Affected 10.11.0 through 10.11.9Affected 11.2.0 through 11.2.1Affected 11.3.0Not affected 11.1.3Not affected 10.11.10Not affected 11.2.2Not affected

References

MMSA-2025-00548vendor-advisory

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