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Vulnerability · Published Jun 12, 2026 · Assigned by Mattermost

CVE-2026-6689*Missing* {{invite_user}} *permission check on team creation allows unprivileged users to set open-invite and allowed-domains team settings*

Medium 4.3

In plain English

A medium-severity missing authorization in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.3Medium
Exploit odds (30 days)0.2%top 95.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/mattermost/mattermost-server11.6.1GHSA-c28q-m4gf-vg4q
Gogithub.com/mattermost/mattermost-server11.5.5GHSA-c28q-m4gf-vg4q
Gogithub.com/mattermost/mattermost-server10.11.17GHSA-c28q-m4gf-vg4q
Gogithub.com/mattermost/mattermost-server10.11.17+incompatible, 11.5.5+incompatible, 11.6.1+incompatibleGO-2026-6283
Gogithub.com/mattermost/mattermost-server/v5no fix listedGO-2026-6283
Gogithub.com/mattermost/mattermost-server/v6no fix listedGO-2026-6283
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260501144115-7d6816abdfd1GO-2026-6283
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260501144115-7d6816abdfd1GHSA-c28q-m4gf-vg4q

Affected products (as reported)

VendorProductVersions
Mattermost Mattermost 11.6.0 – through 11.6.111.5.0 – through 11.5.410.11.0 – through 10.11.1510.11.0 – through 10.11.16

Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

References