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Vulnerability record · CVE-2026-59724 · published 8 July 2026

CVE-2026-59724: Socket engine.io improper input validation vulnerability

Socket · Engine.Io

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.

7.5 CVSS 3.1 High EPSS 0.61% · top 53.0% CWE-20 · Improper input validation
7.5CVSS 3.1 base score
0.61%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
13 Jul 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/socketio/socket.io/commit/1fa1f46cd420ac5b57bb4c04c959b58f3c79158c Patch
https://github.com/socketio/socket.io/releases/tag/[email protected] Release Notes
https://github.com/socketio/socket.io/security/advisories/GHSA-gr94-w7qr-f4j3 PatchVendor AdvisoryMitigation

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-59724), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.