CVE-2026-0999
Medium
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
SeverityMedium
CVSS5.4
Exploit probability—
Product
Mattermost Server
PublishedFeb 16, 2026
First seenFeb 16, 2026
Weakness typeCWE-303CWE-303
How to fix
Update
- mattermost mattermost_server10.11.10, 11.1.3, 11.2.2 or later
- github.com/mattermost/mattermost/server/v88.0.0-20251212052346-61651b0df7ea or later
- github.com/mattermost/mattermost-server5.3.2-0.20251212052346-61651b0df7ea or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.10, 11.1.0 ≤ v < 11.1.3, 11.2.0 ≤ v < 11.2.2 | 10.11.10, 11.1.3, 11.2.2 |
| github.com/mattermost/mattermost/server/v8Go | v < 8.0.0-20251212052346-61651b0df7ea | 8.0.0-20251212052346-61651b0df7ea |
| github.com/mattermost/mattermost-serverGo | 11.1.0 ≤ v, 10.11.0 ≤ v, 11.2.0 ≤ v, v < 5.3.2-0.20251212052346-61651b0df7ea, No range specified, 10.11.0+incompatible ≤ v, 11.1.0+incompatible ≤ v, 11.2.0+incompatible ≤ v | 5.3.2-0.20251212052346-61651b0df7ea |
| github.com/mattermost/mattermost-server/v5Go | No range specified | — |
| github.com/mattermost/mattermost-server/v6Go | No range specified | — |
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