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TI-2026-75214 Aliases CVE-2026-18256GHSA-mqc4-5px9-95jm

Private team metadata disclosure via Mattermost team search API

Priority LOW 19CWE-863Published · Updated

Key facts

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

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-863.

Summary

Mattermost fails to properly restrict private teams from public team search results in versions 11.10.0, 11.7.0 through 11.7.9, 11.9.0 through 11.9.1, and 11.8.0 through 11.8.5. An authenticated user without permission to list private teams can send a modified team search request to disclose the ID, name, and display name of private teams. The weakness is classified as CWE-863 (Incorrect Authorization).

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to properly restrict private teams from public team search results, which allows an authenticated user without permission to list private teams to disclose the ID, name, and display name of private teams via a modified team search request. Mattermost Advisory ID: MMSA-2026-00748

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00162 5th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.11.0, 11.10.1, 11.7.10 +2

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
MattermostMattermost11.10.0 – 11.10.0; 11.7.0 – 11.7.9; 11.9.0 – 11.9.1; 11.8.0 – 11.8.511.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6Patch availableCNA
  • Mattermost VendorMattermost Affected 11.10.0 – 11.10.0; 11.7.0 – 11.7.9; 11.9.0 – 11.9.1; 11.8.0 – 11.8.5 Fixed in 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 Patch available CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*11.7.0 to before 11.7.10; 11.8.0 to before 11.8.6; 11.9.0 to before 11.9.2VulnerableMattermost
cpe:2.3:a:mattermost:mattermost_server:11.10.0:*:*:*:*:*:*:*11.10.0VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 11.7.0 to before 11.7.10; 11.8.0 to before 11.8.6; 11.9.0 to before 11.9.2 Vulnerable ·Mattermost
  • cpe:2.3:a:mattermost:mattermost_server:11.10.0:*:*:*:*:*:*:* Versions 11.10.0 Vulnerable ·Mattermost

Remediation

Mattermost fixed versions are 11.11.0, 11.10.1, 11.7.10, 11.9.2 and 11.8.6, per Mattermost advisory MMSA-2026-00748.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6

Timeline

  1. 2026-10-16 Threatist record created from CVE-2026-18256
  2. 2026-10-16 Alias added: GHSA-mqc4-5px9-95jm

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