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TI-2026-08856 Aliases CVE-2026-10103GHSA-4h7j-7xp4-wp5p

Authorization bypass in Mattermost

Priority LOW 20CWE-639Published · 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. Impact type from CWE-639.

Summary

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify post ownership in the shared channel inbound sync handler, which allows an authenticated remote cluster to modify or delete posts authored by local users or other remotes via crafted sync messages referencing arbitrary post IDs in channels shared with that remote.. Mattermost Advisory ID: MMSA-2026-00689

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00242 15th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.8.0, 11.7.3, 11.6.5 +1

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 – 11.7.2; 11.6.0 – 11.6.4; 10.11.0 – 10.11.1911.8.0, 11.7.3, 11.6.5, 10.11.20Patch availableCNA
  • Mattermost VendorMattermost Affected 11.7.0 – 11.7.2; 11.6.0 – 11.6.4; 10.11.0 – 10.11.19 Fixed in 11.8.0, 11.7.3, 11.6.5, 10.11.20 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*10.11.0 to before 10.11.20; 11.6.0 to before 11.6.5; 11.7.0 to before 11.7.3VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.20; 11.6.0 to before 11.6.5; 11.7.0 to before 11.7.3 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.8.0, 11.7.3, 11.6.5, 10.11.20

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-10103
  2. 2026-10-03 Alias added: GHSA-4h7j-7xp4-wp5p

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