Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-08T15:35:39 engine.io: Engine.IO: Denial of Service via crafted WebTransport session ID 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CWE-843

Socket.IO enables bidirectional and low-latency communication for every platform. From 6.5.0 before 6.6.7, Engine.IO servers with WebTransport enabled can resolve a crafted session ID such as __proto__ through an inherited property of the clients object during WebTransport upgrade handling, causing a TypeError and denial of service. This issue is fixed in version 6.6.7.

A flaw was found in Engine.IO. When Engine.IO servers have WebTransport enabled, a remote attacker can craft a session ID to resolve an inherited property of the clients object during WebTransport upgrade handling. This can lead to a TypeError, resulting in a denial of service (DoS) for the server. This vulnerability impacts the availability of the service.

This flaw has been rated as Important. When Engine.IO servers have WebTransport enabled, a remote attacker can trigger a denial of service. This occurs by sending a crafted session ID that resolves an inherited property during WebTransport upgrade handling, leading to a TypeError and impacting service availability. Red Hat Hardened Images 2026-06-18T00:00:00Z RHSA-2026:26994 dotnet8-0-main-8.0.128-1.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-2026-59724 https://nvd.nist.gov/vuln/detail/CVE-2026-59724 https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.7 https://github.com/socketio/socket.io/security/advisories/GHSA-gr94-w7qr-f4j3