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
Published: 2026-10-16
Score: 6.5 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

No analysis available yet.

Remediation

Vendor Solution

Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.

Tracking

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Advisories

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References
Link Providers
https://mattermost.com/security-updates cve-icon cve-icon
History

Fri, 16 Oct 2026 07:15:00 +0000

Type Values Removed Values Added
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
Title Mattermost guest account privilege escalation via member roles API
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N'}

Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-10-16T06:56:51.996Z

Reserved: 2026-07-31T23:37:44.233Z

Link: CVE-2026-18551

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-16T07:17:12.260

Modified: 2026-10-16T07:17:12.260

Link: CVE-2026-18551

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses