Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-08T15:37:52 socket.io: engine.io: Socket.IO: Denial of Service via invalid binary POST requests 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CWE-772

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.

A flaw was found in Socket.IO, specifically within the Engine.IO protocol v4 polling transport. An unauthenticated attacker can exploit this vulnerability by sending invalid binary POST requests with a Content-Type of application/octet-stream. This improper handling of requests prevents the HTTP response from being properly closed, which can lead to the exhaustion of server-side connections and sockets. The primary consequence is a Denial of Service (DoS), making the affected service unavailable to legitimate users.

This flaw has been rated as Important. An unauthenticated remote attacker can exploit a vulnerability in the Engine.IO protocol v4 polling transport of Socket.IO by sending malformed binary POST requests. This can lead to server-side connection exhaustion and a denial of service, impacting the availability of applications utilizing Socket.IO. Red Hat Hardened Images 2026-07-10T00:00:00Z RHSA-2026:37577 dotnet8-0-main-8.0.128-1.1.hum1 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-cuda-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-gaudi-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/bootc-rocm-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Affected rhelai3/disk-image-cuda-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-59725 https://nvd.nist.gov/vuln/detail/CVE-2026-59725 https://github.com/socketio/socket.io/commit/fc11285e14964c2132d122164bf130c355f60671 https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7 https://github.com/socketio/socket.io/security/advisories/GHSA-r635-g3xr-vw7x