Read the docs
TI-2026-08408 Aliases CVE-2026-9571GHSA-4v7j-4mvr-5975

Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost

Priority LOW 31CWE-305Published · Updated

Key facts

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

Attack profile from CVSS 3.1 · NVD. Fix status from CNA.

Summary

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon user account deactivation, which allows a deactivated user or an attacker in possession of a valid refresh token to obtain new functional access tokens via the OAuth refresh token grant endpoint.. Mattermost Advisory ID: MMSA-2026-00680

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00303 23rd 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
Total

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-2026-9571
  2. 2026-10-03 Alias added: GHSA-4v7j-4mvr-5975

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