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TI-2026-10984 Aliases CVE-2026-12882GHSA-mfv9-qx66-gxm4

Mattermost Markdown autolink parsing denial of service

Priority LOW 20CWE-407Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-407.

Summary

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to parse Markdown autolinks with unmatched trailing closing parentheses in linear time, which allows an authenticated user with permission to create posts to cause excessive server CPU consumption and degrade availability for other users via specially crafted post or message attachment content. Mattermost Advisory ID: MMSA-2026-00703

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00367 30th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.10.0, 11.9.1, 11.8.5 +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
MattermostMattermost11.9.0 – 11.9.0; 11.8.0 – 11.8.4; 11.7.0 – 11.7.7; 10.11.0 – 10.11.2211.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23Patch availableCNA
  • Mattermost VendorMattermost Affected 11.9.0 – 11.9.0; 11.8.0 – 11.8.4; 11.7.0 – 11.7.7; 10.11.0 – 10.11.22 Fixed in 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*10.11.0 to before 10.11.23; 11.7.0 to before 11.7.8; 11.8.0 to before 11.8.5; 11.9.0 to before 11.9.1VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.23; 11.7.0 to before 11.7.8; 11.8.0 to before 11.8.5; 11.9.0 to before 11.9.1 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-12882
  2. 2026-10-03 Alias added: GHSA-mfv9-qx66-gxm4

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