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Description

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.

PUBLISHED Reserved 2026-07-06 | Published 2026-07-08 | Updated 2026-07-08 | Assigner GitHub_M




HIGH: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-20: Improper Input Validation

Product status

>= 6.5.0, < 6.6.7
affected

References

github.com/...ket.io/security/advisories/GHSA-gr94-w7qr-f4j3

github.com/...ommit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c

github.com/socketio/socket.io/releases/tag/engine.io@6.6.7

cve.org (CVE-2026-59724)

nvd.nist.gov (CVE-2026-59724)

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