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CVE-2026-18551

6.5 medium SSVC exploitation: none Published
NVD · CVE.org

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

Fix

Nothing published yet: no patch, vendor advisory or mitigation reference on NVD, no vendor advisory in the News for this CVE, not in CISA's KEV, no fixed package version. BaselineWatch does not guess at one.

Change history 3

  1. StatusUndergoing Analysis → PublishedNVD modified 2026-10-20 13:11
  2. StatusReceived → Undergoing AnalysisNVD modified 2026-10-17 04:16
  3. First seenCVSS 6.5NVD modified 2026-10-16 07:17

Affected (CPE criteria) 0

NVD has not attached CPE configurations yet.

References 1