Input validation error in socket.io - CVE-2026-59724
Published: June 25, 2026
Vulnerability identifier: #VU135352
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-59724
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper input validation in WebTransport upgrade handling when processing a crafted WebTransport upgrade request with a chosen session ID. A remote attacker can send a specially crafted WebTransport upgrade request to cause a denial of service.
Only deployments with WebTransport support enabled are vulnerable. WebTransport is not enabled by default.
Affected software
socket.io
How to mitigate CVE-2026-59724
Install security update from vendor's website.
socket.io - update to 6.6.7