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TI-2026-05868 Aliases CVE-2026-6689GHSA-c28q-m4gf-vg4q

Missing authorization in Mattermost

Priority LOW 19CWE-862Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-862.

Summary

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

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00152 4th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.7.0, 11.6.2, 11.5.5 +2github.com/mattermost/mattermost-server (Go): 11.6.1, 11.5.5, 10.11.17+1 more product

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MattermostMattermost11.6.0 – 11.6.1; 11.5.0 – 11.5.4; 10.11.0 – 10.11.15; 10.11.0 – 10.11.1611.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17Patch availableCNA
—github.com/mattermost/mattermost-server (Go)11.6.0 to before 11.6.111.6.1Patch availableGHSA-c28q-m4gf-vg4q
—github.com/mattermost/mattermost-server (Go)11.5.0 to before 11.5.511.5.5Patch availableGHSA-c28q-m4gf-vg4q
—github.com/mattermost/mattermost-server (Go)10.11.0 to before 10.11.1710.11.17Patch availableGHSA-c28q-m4gf-vg4q
—github.com/mattermost/mattermost/server/v8 (Go)8.0.0-20250731163400-5b955468ea1e to before 8.0.0-20260501144115-7d6816abdfd18.0.0-20260501144115-7d6816abdfd1Patch availableGHSA-c28q-m4gf-vg4q
  • Mattermost VendorMattermost Affected 11.6.0 – 11.6.1; 11.5.0 – 11.5.4; 10.11.0 – 10.11.15; 10.11.0 – 10.11.16 Fixed in 11.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17 Patch available CNA
  • github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.6.0 to before 11.6.1 Fixed in 11.6.1 Patch available GHSA-c28q-m4gf-vg4q
  • github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.5.0 to before 11.5.5 Fixed in 11.5.5 Patch available GHSA-c28q-m4gf-vg4q
  • github.com/mattermost/mattermost-server (Go) Vendor— Affected 10.11.0 to before 10.11.17 Fixed in 10.11.17 Patch available GHSA-c28q-m4gf-vg4q
  • github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 8.0.0-20250731163400-5b955468ea1e to before 8.0.0-20260501144115-7d6816abdfd1 Fixed in 8.0.0-20260501144115-7d6816abdfd1 Patch available GHSA-c28q-m4gf-vg4q

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*10.11.0 to before 10.11.17; 11.5.0 to before 11.5.5; 11.6.0 to before 11.6.2VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.17; 11.5.0 to before 11.5.5; 11.6.0 to before 11.6.2 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17
  • Fix · GHSA-c28q-m4gf-vg4q github.com/mattermost/mattermost-server (Go) Fixed in 11.6.1 Advisory →
  • Fix · GHSA-c28q-m4gf-vg4q github.com/mattermost/mattermost-server (Go) Fixed in 11.5.5 Advisory →
  • Fix · GHSA-c28q-m4gf-vg4q github.com/mattermost/mattermost-server (Go) Fixed in 10.11.17 Advisory →
  • Fix · GHSA-c28q-m4gf-vg4q github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20260501144115-7d6816abdfd1 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-6689
  2. 2026-10-03 Alias added: GHSA-c28q-m4gf-vg4q

References

Advisory 2

Other 15

  • TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
  • TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
  • TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
  • TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
  • TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
  • TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
See all 505 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences