Vulnerability Details CVE-2026-95666
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771
Exploit prediction scoring system (EPSS) score
EPSS Score 0.004
EPSS Ranking 27.6%
CVSS Severity
CVSS v3 Score 4.3
References
Products affected by CVE-2026-95666
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cpe:2.3:a:mattermost:mattermost_server:11.10.0
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cpe:2.3:a:mattermost:mattermost_server:11.10.1
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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
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cpe:2.3:a:mattermost:mattermost_server:11.8.4
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cpe:2.3:a:mattermost:mattermost_server:11.8.5