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TI-2026-75216 Aliases CVE-2026-18560GHSA-3m39-x8xr-762f

Mattermost GetFile API lets users infer quarantined post status

Priority LOW 19CWE-203Published · Updated

Key facts

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

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-203.

Summary

Mattermost 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 check user permissions after other validations in the GetFile API. This observable discrepancy (CWE-203) lets an authenticated user who is not a content reviewer infer whether a post has been flagged.

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 validate user’s permissions before other validations which allows non-content reviewers to infer a post’s flagged status via direct API call.. Mattermost Advisory ID: MMSA-2026-00754

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0018 7th 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

Upgrade Mattermost to 11.11.0, 11.10.1, 11.7.10, 11.9.2 or 11.8.6, the fixed versions listed for each release line, as described in Mattermost advisory MMSA-2026-00754.

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-2026-18560
  2. 2026-10-16 Alias added: GHSA-3m39-x8xr-762f

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