Is CVE-2026-16453 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-16453?

CVE-2026-16453 has a CVSS v3 severity of HIGH (7.1).

Back

CVE-2026-16453

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