Description
Mattermost versions 10.11.x <= 10.11.5, 11.0.x <= 11.0.4, 10.12.x <= 10.12.2 fail to invalidate remote cluster invite tokens when using the legacy (version 1) protocol or when the confirming party does not provide a refreshed token, which allows an attacker who has obtained an invite token to authenticate as the remote cluster and perform limited actions on shared channels even after the invitation has been legitimately confirmed.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 10.11.0 – ≤ 10.11.5, 11.0.0 – ≤ 11.0.4, 10.12.0 – ≤ 10.12.2 | 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 | >= 10.12.0, < 10.12.2 | 10.12.2 | GHSA-x3r8-2hmh-89f5 |
| Go | github.com/mattermost/mattermost | >= 10.11.0-rc1, < 10.11.5 | 10.11.5 | GHSA-x3r8-2hmh-89f5 |
| Go | github.com/mattermost/mattermost | >= 11.0.0-alpha.1, < 11.0.4 | 11.0.4 | GHSA-x3r8-2hmh-89f5 |
| Go | github.com/mattermost/mattermost | >= 10.11.0-rc1+incompatible, < 10.11.5+incompatible · >= 10.12.0+incompatible, < 10.12.2+incompatible · >= 11.0.0-alpha.1+incompatible, < 11.0.4+incompatible | 10.11.5+incompatible, 10.12.2+incompatible, 11.0.4+incompatible | GO-2025-4256 |
| Go | github.com/mattermost/mattermost-server | < 11.0.4 | 11.0.4 | GHSA-x3r8-2hmh-89f5 |
| Go | github.com/mattermost/mattermost-server | < 11.0.4+incompatible | 11.0.4+incompatible | GO-2025-4256 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2025-4256 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2025-4256 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20251031095924-e7e23b94e006 | 8.0.0-20251031095924-e7e23b94e006 | GHSA-x3r8-2hmh-89f5 |
Advisories 2
- 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