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TI-2026-08496 Aliases CVE-2026-9693GHSA-f5mp-j4vf-9jp4

Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite

Priority LOW 16CWE-459Published · Updated

Key facts

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

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00271 19th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.9.0, 10.11.21, 11.7.6

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
MattermostMattermost10.11.0 – 10.11.20; 11.7.0 – 11.7.511.9.0, 10.11.21, 11.7.6Patch availableCNA
  • Mattermost VendorMattermost Affected 10.11.0 – 10.11.20; 11.7.0 – 11.7.5 Fixed in 11.9.0, 10.11.21, 11.7.6 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*10.11.0 to before 10.11.21; 11.7.0 to before 11.7.6VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.21; 11.7.0 to before 11.7.6 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.9.0, 10.11.21, 11.7.6

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-9693
  2. 2026-10-03 Alias added: GHSA-f5mp-j4vf-9jp4

References

Advisory 1

  • 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