CVE-2026-59724

Socket.IO: Engine.IO WebTransport SID DoS

CVSS 7.5 HIGHEPSS 0.3%CWE-20

Vexday Risk Score

21Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 7.5EPSS 0.3%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

08 Jul 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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.

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

Affected products

socketio · socket.io

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