Vulnerability Details CVE-2026-16047
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
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 5.8%
CVSS Severity
CVSS v3 Score 4.3
References
Products affected by CVE-2026-16047
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cpe:2.3:a:mattermost:mattermost_server:11.7.0
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cpe:2.3:a:mattermost:mattermost_server:11.7.1
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cpe:2.3:a:mattermost:mattermost_server:11.7.2
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cpe:2.3:a:mattermost:mattermost_server:11.7.3
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cpe:2.3:a:mattermost:mattermost_server:11.7.4
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cpe:2.3:a:mattermost:mattermost_server:11.7.5
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cpe:2.3:a:mattermost:mattermost_server:11.7.6
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cpe:2.3:a:mattermost:mattermost_server:11.8.0
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cpe:2.3:a:mattermost:mattermost_server:11.8.1
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cpe:2.3:a:mattermost:mattermost_server:11.8.2
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cpe:2.3:a:mattermost:mattermost_server:11.8.3