Improper input validation in Socket Engine.io
CVE-2026-59724
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.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (47.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 48th percentile — 47.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Socket Engine.io
- Socketio Socket.io — versions >= 6.5.0, < 6.6.7
Weakness classification (CWE)
References
- github.com/socketio/socket.io/security/advisories/GHSA-gr94-w7qr-f4j3 (Patch, Mitigation, Vendor Advisory)
- github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c (Patch)
- github.com/socketio/socket.io/releases/tag/engine.io@6.6.7 (Release Notes)
Frequently asked questions
- What is CVE-2026-59724?
- CVE-2026-59724 is a high-severity vulnerability in Socket Engine.io, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2026-07-08.
- How severe is CVE-2026-59724?
- High severity. CVSS v3 base score is 7.5 out of 10.