Socket.IO: Engine.IO WebTransport SID DoS — GHSA-GR94-W7QR-F4J3

Summary

### Impact Engine.IO servers with **WebTransport enabled** are vulnerable to a remotely triggerable denial of service. A malicious unauthenticated client can send a crafted WebTransport upgrade request containing a specially chosen session ID, such as `__proto__`. Because the session ID lookup did not properly verify that the key was an own property of the clients object, the lookup could resolve to an inherited…

Timeline

Published by source

2026-08-31

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 7.5 out of 10.
• Reported EPSS value: 0.00609.
• Review exposure for the affected product or family: npm: engine.io.

Product

npm: engine.io

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-GR94-W7QR-F4J3

Source

GitHub

Vendor

GitHub

Published by source

2026-08-31

Last source activity

2026-08-31

Additional identifiers

CVE-2026-59724

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.