Mattermost doesn't enforce PermissionInviteUser when setting AllowOpenInvite or AllowedDomains during team creation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-6689: 0.15% estimated exploitation activity in the next 30 days; percentile 4.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 allowopeninvite: true and/or a non-empty alloweddomains in the request body.. Mattermost Advisory ID: MMSA-2026-00655

Published by the source

25 Aug 2026, 19:43 UTC

Last modified by the source

26 Aug 2026, 01:19 UTC

Source last checked

26 Oct 2026, 15:28 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-c28q-m4gf-vg4q

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GO-2026-6283

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# Patch Next advisory brief: CVE-2026-6689

Advisory: Mattermost doesn't enforce PermissionInviteUser when setting AllowOpenInvite or AllowedDomains during team creation
IDs: CVE-2026-6689, GHSA-c28q-m4gf-vg4q
Record: https://patchnext.com/advisories/cve-2026-6689 (revision 2, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/mattermost/mattermost/server/v8 8.0.0-20260501144115-7d6816abdfd1; github.com/mattermost/mattermost-server 11.6.1, 11.5.5, 10.11.17. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mattermost/mattermost/server/v8: affected >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260501144115-7d6816abdfd1; fixed in 8.0.0-20260501144115-7d6816abdfd1
- Go github.com/mattermost/mattermost-server/v6: affected every version
- Go github.com/mattermost/mattermost-server: affected >= 11.6.0, <= 11.6.0; >= 11.5.0, <= 11.5.4; >= 10.11.0, <= 10.11.15; fixed in 10.11.17, 11.5.5, 11.6.1
- Go github.com/mattermost/mattermost-server/v5: affected every version

## Suggested inspection (read-only)
- Go github.com/mattermost/mattermost/server/v8: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server/v6: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server/v5: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server/v6, github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6283 (OSV record GO-2026-6283 lists affected ranges: Go github.com/mattermost/mattermost-server >=10.11.0+incompatible =11.5.0+incompatible =11.6.0+incompatible =0; Go github.com/mattermost/mattermost-server/v6 >=0; Go github.com/mattermost/mattermost/server/v8 >=8.0.0-20250731163400-5b955468ea1e <8.0.0-20260501144115-7d6816abdfd1 (fixed))
- Verified: https://github.com/advisories/GHSA-c28q-m4gf-vg4q (GitHub-reviewed advisory GHSA-c28q-m4gf-vg4q lists affected ranges: Go github.com/mattermost/mattermost-server >=11.6.0 =11.5.0 =10.11.0 =8.0.0-20250731163400-5b955468ea1e <8.0.0-20260501144115-7d6816abdfd1)

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