CVE-2026-59725 PUBLISHED

Socket.IO enables bidirectional and low-latency communication for every platform. From 4.1.0 before 6.6.7, Engine.IO protocol v4 polling transport does not properly close the HTTP response for invalid binary POST requests with Content-Type: application/octet-stream, allowing an unauthenticated attacker to exhaust server-side connections and sockets. This issue is fixed in version 6.6.7.

• https://github.com/socketio/socket.io/security/advisories/GHSA-r635-g3xr-vw7x
• https://github.com/socketio/socket.io/commit/fc11285e14964c2132d122164bf130c355f60671
• https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7

• CWE-404: Improper Resource Shutdown or Release CWE