Description
Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 10.11.0 – ≤ 10.11.3, 10.5.0 – ≤ 10.5.11 | 11.0.0 |
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 | < 5.3.2-0.20250905150616-ba86dfc5876b | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost | all versions | — | GO-2025-4122 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.4 | 10.11.4 | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server | >= 10.5.0, < 10.5.12 | 10.5.12 | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server | < 5.3.2-0.20250905150616-ba86dfc5876b | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server | >= 10.5.0+incompatible, < 10.5.12+incompatible · >= 10.11.0+incompatible, < 10.11.4+incompatible | 10.5.12+incompatible, 10.11.4+incompatible | GO-2025-4122 |
| Go | github.com/mattermost/mattermost-server/v5 | < 5.3.2-0.20250905150616-ba86dfc5876b | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2025-4122 |
| Go | github.com/mattermost/mattermost-server/v6 | < 5.3.2-0.20250905150616-ba86dfc5876b | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2025-4122 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20250905150616-ba86dfc5876b | 8.0.0-20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20251212204551-54f2e9b4afd5 | 8.0.0-20251212204551-54f2e9b4afd5 | GO-2025-4122 |
| Go | github.com/mattermost/mattermost/v5 | all versions | — | GO-2025-4122 |
Advisories 3
- 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
- WID-SEC-2025-2315 Mattermost Server und Mobile: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 27, 2025