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CVE-2026-0999 Moderate

Mattermost fails to properly validate login method restrictions in github.com/mattermost/mattermost-server

Mattermost fails to properly validate login method restrictions in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: github.com/mattermost/mattermost-server/v5 before v5.3.2-0.20251212052346-61651b0df7ea.

Exploit probability 0.2%
Published February 23, 2026
Required by Not available
Last source change February 23, 2026

02 / AFFECTED SOFTWARE

Affected packages

Unknown Unknown

34 explicit affected versions

Go github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost/server/v8
Go github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server/v5
Go github.com/mattermost/mattermost-server/v6
Go github.com/mattermost/mattermost/server/v8

03 / CONNECTIONS

Connected vulnerabilities

related OPENSUSE-SU-2026:21483-1

04 / EVIDENCE

Source records

Open Source Vulnerabilities CVE-2026-0999

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

View original source
Open Source Vulnerabilities GHSA-3c9r-7f29-qp32

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

View original source
Open Source Vulnerabilities GO-2026-4520

Mattermost fails to properly validate login method restrictions in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: github.com/mattermost/mattermost-server/v5 before v5.3.2-0.20251212052346-61651b0df7ea.

View original source

05 / REFERENCES

Further evidence