Vulnerability Details CVE-2026-21388
Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 4.9%
CVSS Severity
CVSS v3 Score 3.7
References
Products affected by CVE-2026-21388
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cpe:2.3:a:mattermost:mattermost_server:-
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cpe:2.3:a:mattermost:mattermost_server:0.5.0
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cpe:2.3:a:mattermost:mattermost_server:0.6.0
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cpe:2.3:a:mattermost:mattermost_server:1.0.0
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cpe:2.3:a:mattermost:mattermost_server:1.1.0
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cpe:2.3:a:mattermost:mattermost_server:1.1.1
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cpe:2.3:a:mattermost:mattermost_server:1.2.0
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cpe:2.3:a:mattermost:mattermost_server:1.2.1
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cpe:2.3:a:mattermost:mattermost_server:1.3.0
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cpe:2.3:a:mattermost:mattermost_server:1.4.0
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cpe:2.3:a:mattermost:mattermost_server:2.0.0
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cpe:2.3:a:mattermost:mattermost_server:2.1.0
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cpe:2.3:a:mattermost:mattermost_server:2.2.0