CVE-2026-18223
Published:October 16, 2026
Updated:October 21, 2026
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
Affected Packages
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) =v11.10.0 <v11.10.1Fix Suggestion:
Update to version v11.10.1Related Resources (2)
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Contact UsCVSS v4
Base Score:
5.9
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
HIGH
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Incorrect Authorization
EPSS
Base Score:
0.16