Is CVE-2026-9820 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-9820?

CVE-2026-9820 has a CVSS v3 severity of LOW (3.8).

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CVE-2026-9820

Description

Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the User Manager role to obtain invite links for private teams and use them to join or share access to those teams via the scheme teams API endpoint.. Mattermost Advisory ID: MMSA-2026-00671