MinorCritical vulnerability

CVE-2026-16453 (CVSS 7.1)

NVD · officialPublished Oct 16, 2026Risk 23/100EPSS 0.2%

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

Technical details

CVSS

7.1

AV:NetworkAC:LowPR:LowUI:NoneC:HighI:LowA:None

Evidence and sources

This record is attributed to NVD. Exploitation status and remediation guidance are kept separate from the vulnerability's technical severity.

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