Description
Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.0.0 – ≤ 11.0.2, 10.12.0 – ≤ 10.12.1, 10.11.0 – ≤ 10.11.4, 10.5.0 – ≤ 10.5.12 | 11.1.0 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260723T184607-160000.1.1 | openSUSE-SU-2026:21483-1 |
| openSUSE Leap 15.6 | govulncheck-vulndb | 0.0.20251230T014957-150000.1.134.1 | SUSE-SU-2026:0037-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | >= 11.0.0, < 11.0.3 | 11.0.3 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | >= 10.12.0, < 10.12.2 | 10.12.2 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.5 | 10.11.5 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | >= 10.5.0, < 10.5.13 | 10.5.13 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | all versions | — | GO-2025-4170 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2025-4170 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2025-4170 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20251022210333-acda1fb5dd46 | 8.0.0-20251022210333-acda1fb5dd46 | GHSA-mp6x-97xj-9x62 |
Advisories 4
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- SUSE-SU-2026:0037-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Mar 23, 2026
- NCSC-2025-0378 Kwetsbaarheden verholpen in Mattermost NCSC-NL (Netherlands) · Nov 28, 2025
- WID-SEC-2025-2434 Mattermost Server: Mehrere Schwachstellen ermöglichen die Umgehung von Sicherheitsmaßnahmen BSI CERT-Bund (WID) · Nov 27, 2025