Is CVE-2026-16047 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-16047?

CVE-2026-16047 has a CVSS v3 severity of MEDIUM (4.3).

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CVE-2026-16047

Description

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674