Improper Resource Shutdown or Release in socket.io - CVE-2026-59725
Published: June 25, 2026
Vulnerability identifier: #VU135351
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-2026-59725
CWE-ID: CWE-404
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 resource shutdown or release in the Engine.IO polling transport when handling invalid binary POST requests for Engine.IO protocol v4. A remote attacker can open polling sessions and send a specially crafted request to cause a denial of service.
The issue occurs when the server reports a transport error but does not properly close the HTTP response, which can leave the underlying connection open and consume server-side sockets or file descriptors.
Affected software
socket.io
How to mitigate CVE-2026-59725
Install security update from vendor's website.
socket.io - update to 6.6.7