CVE-2026-59725: Socket Engine.io

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

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.

Affected products

• Socket Engine.io: from 4.1.0, before 6.6.7 (fixed in 6.6.7)

Published 2026-07-08. Last modified 2026-07-13.