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CVE-2026-18223 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 invited recipient's email address when redeeming team and guest invitation tokens, which allows an authenticated attacker to join a team or gain unauthorized access to private channels via a forwarded or leaked invitation link.. Mattermost Advisory ID: MMSA-2026-00747

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:5 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N

References to Advisories, Solutions, and Tools

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

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-863	Incorrect Authorization	[email protected]

Affected Products

Product	Versions
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

3 change records found show changes

Date	Action	Recorded By
Oct 29, 2026	Initial Analysis	[email protected]
Oct 16, 2026	CVE Modified	CISA-ADP
Oct 16, 2026	New CVE Received	[email protected]