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TI-2026-13254 Aliases CVE-2026-15754GHSA-mg83-f953-3vq5

Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal

Priority LOW 19CWE-863Published · Updated

Key facts

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

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

Summary

Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00246 15th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.9.0, 11.7.7, 11.8.4

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
MattermostMattermost11.7.0 – 11.7.6; 11.8.0 – 11.8.311.9.0, 11.7.7, 11.8.4Patch availableCNA
  • Mattermost VendorMattermost Affected 11.7.0 – 11.7.6; 11.8.0 – 11.8.3 Fixed in 11.9.0, 11.7.7, 11.8.4 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*11.7.0 to before 11.7.7; 11.8.0 to before 11.8.4VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 11.7.0 to before 11.7.7; 11.8.0 to before 11.8.4 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.9.0, 11.7.7, 11.8.4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-15754
  2. 2026-10-03 Alias added: GHSA-mg83-f953-3vq5

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