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TI-2026-13431 Aliases CVE-2026-16049GHSA-vr3j-2q9w-h26r

Missing authorization in Mattermost

Priority LOW 18CWE-862Published · 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-862.

Summary

Mattermost Plugins versions <=11.8 10.20.11 11.5.7.0 _The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied_ {{post_id}}_, and fails to validate the_ {{web_url}} _parameter against the configured GitLab instance, which allows an authenticated attacker to inject bot-authored messages containing arbitrary URLs into channels they do not have access to via the_ {{createIssue}} _and_ {{attachCommentToIssue}} _API endpoints._ Mattermost Advisory ID: MMSA-2026-00673

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00294 22nd 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
MattermostMattermostup to 10.20.11; up to 11.5.711.9.0, 10.11.21, 11.7.6Patch availableCNA
  • Mattermost VendorMattermost Affected up to 10.20.11; up to 11.5.7 Fixed in 11.9.0, 10.11.21, 11.7.6 Patch available CNA

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-2026-16049
  2. 2026-10-03 Alias added: GHSA-vr3j-2q9w-h26r

References

Advisory 1

  • TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
  • TI-2019-15071 An issue was discovered in Mattermost Packages before 5.16.3. CVSS 3.1CRITICAL 9.8
  • TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
  • TI-2019-15074 An issue was discovered in Mattermost Desktop App before 4.3.0 on macOS. CVSS 3.1CRITICAL 9.8
  • 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
See all 670 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences