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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…

Medium CVSS 6.5
CVECVE-2026-18551
First seen2026-10-16 08:16 UTC
Disclosed2026-10-16 07:17 UTC
Last updated2026-10-16 13:15 UTC
Channel statusauto

Summary

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

In-depth triage

No in-depth report has been generated yet (DR-003 v2 AI pipeline is under construction).

Sources

  • NVD DATABASE

Original Links

Timeline

  1. nvd_ingest NVD