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VULNERABILITIES

CVE-2026-18551 Details

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

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:6.5 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://mattermost.com/security-updates [email protected]Vendor Advisory

Weakness Enumeration

CWE-IDCWE NameSource
CWE-863Incorrect Authorization[email protected]

Affected Products

ProductVersions
mattermost mattermost server
>= 11.7.0, < 11.7.10
>= 11.8.0, < 11.8.6
>= 11.9.0, < 11.9.2
11.10.0

CPE

  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
  • cpe:2.3:a:mattermost:mattermost_server:11.10.0:*:*:*:*:*:*:*

Remediation

  • No remediation found in references.

Change History

5 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-18551
NVD Published Date:
Oct 16, 2026
NVD Last Modified:
Oct 29, 2026
Source:
[email protected]
CVE-2026-18551 Details - Not Deferred