Description
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 Fail to enforce PermissionInviteUser when setting AllowOpenInvite or AllowedDomains during team creation (the check was only applied on update/patch), which allows an authenticated user holding PermissionCreateTeam but not PermissionInviteUser on the resulting team to configure invite-controlled team settings (make the team publicly joinable via open invite and/or constrain membership via allowed domains) that they are not permitted to set on an existing team via POST /api/v4/teams with allow_open_invite: true and/or a non-empty allowed_domains in the request body.. Mattermost Advisory ID: MMSA-2026-00655
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 – ≤ 11.6.1, 11.5.0 – ≤ 11.5.4, 10.11.0 – ≤ 10.11.15, 10.11.0 – ≤ 10.11.16 | 11.7.0 |
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.
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | govulncheck-vulndb | 0.0.20260827T195228-160000.1.1 | SUSE-SU-2026:23625-1 |
| SLES 16.0 | govulncheck-vulndb | 0.0.20260827T195228-160000.1.1 | SUSE-SU-2026:23625-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260827T195228-160000.1.1 | openSUSE-SU-2026:21761-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | >= 11.6.0, < 11.6.1 | 11.6.1 | GHSA-c28q-m4gf-vg4q |
| Go | github.com/mattermost/mattermost-server | >= 11.5.0, < 11.5.5 | 11.5.5 | GHSA-c28q-m4gf-vg4q |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.17 | 10.11.17 | GHSA-c28q-m4gf-vg4q |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0+incompatible, < 10.11.17+incompatible · >= 11.5.0+incompatible, < 11.5.5+incompatible · >= 11.6.0+incompatible, < 11.6.1+incompatible | 10.11.17+incompatible, 11.5.5+incompatible, 11.6.1+incompatible | GO-2026-6283 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2026-6283 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2026-6283 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260501144115-7d6816abdfd1 | 8.0.0-20260501144115-7d6816abdfd1 | GHSA-c28q-m4gf-vg4q |
Advisories 3
- SUSE-SU-2026:23625-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Sep 29, 2026
- openSUSE-SU-2026:21761-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Sep 9, 2026
- WID-SEC-2026-1529 Mattermost Server: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · Jun 14, 2026
References
- MMSA-2026-00655 vendor-advisory