Vulnerability Details CVE-2026-59724
Socket.IO enables bidirectional and low-latency communication for every platform. From 6.5.0 before 6.6.7, Engine.IO servers with WebTransport enabled can resolve a crafted session ID such as __proto__ through an inherited property of the clients object during WebTransport upgrade handling, causing a TypeError and denial of service. This issue is fixed in version 6.6.7.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.003
EPSS Ranking 25.9%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-59724
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cpe:2.3:a:socket:engine.io:6.5.0
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cpe:2.3:a:socket:engine.io:6.5.1
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cpe:2.3:a:socket:engine.io:6.5.2
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cpe:2.3:a:socket:engine.io:6.5.3
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cpe:2.3:a:socket:engine.io:6.5.4
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cpe:2.3:a:socket:engine.io:6.5.5
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cpe:2.3:a:socket:engine.io:6.6.0
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cpe:2.3:a:socket:engine.io:6.6.1
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cpe:2.3:a:socket:engine.io:6.6.2
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cpe:2.3:a:socket:engine.io:6.6.3
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cpe:2.3:a:socket:engine.io:6.6.4
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cpe:2.3:a:socket:engine.io:6.6.5
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cpe:2.3:a:socket:engine.io:6.6.6