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CVE PROGRAM SOURCE RECORD6.5 Medium

CVE-2026-18551

Mattermost guest account privilege escalation via member roles API

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Status
Published
Published
Updated
Assigning organization
Mattermost

Description

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 the combination of guest and admin scheme roles which allows an authenticated attacker to escalate a guest account to team or channel admin via a crafted PUT request to the member roles API endpoint.. Mattermost Advisory ID: MMSA-2026-00752

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Mattermost Mattermost

Default version status: unaffected

  • 11.10.0 to ≤ 11.10.0affected
  • 11.7.0 to ≤ 11.7.9affected
  • 11.9.0 to ≤ 11.9.1affected
  • 11.8.0 to ≤ 11.8.5affected
  • 11.11.0unaffected
  • 11.10.1unaffected
  • 11.7.10unaffected
  • 11.9.2unaffected
  • 11.8.6unaffected

References