CVE-2026-0999

MEDIUM5.4EPSS 0.05%

Mattermost fails to properly validate login method restrictions

Published: 2/16/2026Modified: 4/1/2026

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

Affected packages (6)

Go/github.com/mattermost/mattermost-server>= 11.1.0
Go/github.com/mattermost/mattermost-serverfrom 0
Go/github.com/mattermost/mattermost-server/v5from 0
Go/github.com/mattermost/mattermost-server/v6from 0
Go/github.com/mattermost/mattermost/server/v8from 0, < 8.0.0-20251212052346-61651b0df7ea
Go/github.com/mattermost/mattermost/server/v8from 0, < 8.0.0-20251212052346-61651b0df7ea

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 3.1	MEDIUM5.4	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

References (5)

ADVISORYhttps://github.com/advisories/GHSA-3c9r-7f29-qp32
ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-0999
PATCHhttps://github.com/mattermost/mattermost
WEBhttps://github.com/mattermost/mattermost/commit/61651b0df7ea5db55d1e54f8d6fb5fce4149309c
WEBhttps://mattermost.com/security-updates