CVE-2026-59724

EUVD-2026-42312
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
7.5 HIGH
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Awaiting analysis
This vulnerability is currently awaiting analysis.
Base Score
CVSS 3.x
EPSS Score
Percentile: Unknown
Common Weakness Enumeration
References
https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c
https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7
https://github.com/socketio/socket.io/security/advisories/GHSA-gr94-w7qr-f4j3