CVE-2026-16453
Published:October 16, 2026
Updated:October 18, 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 verify the integrity of the SAML RelayState POST parameter which allows an authenticated SAML user to join any team, including invite-only teams, via forging the team_id or invite_id fields in the RelayState.. Mattermost Advisory ID: MMSA-2026-00727
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:
7.1
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
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:
7.1
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
External Control of Assumed-Immutable Web Parameter
EPSS
Base Score:
0.19