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
References
History

Fri, 23 Oct 2026 10:30:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Fri, 16 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 16 Oct 2026 07:30:00 +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 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
Title Mattermost SAML RelayState forgery allows unauthorized team membership
Weaknesses CWE-472
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published: 2026-10-16T07:08:48.627Z

Updated: 2026-10-16T14:18:12.181Z

Reserved: 2026-07-21T10:00:44.943Z

Link: CVE-2026-16453

cve-icon Vulnrichment

Updated: 2026-10-16T14:17:55.882Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-16T08:17:12.640

Modified: 2026-10-16T19:23:18.623

Link: CVE-2026-16453

cve-icon Redhat

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