CVE-2026-59724: CWE-20: Improper Input Validation in socketio socket.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.
AI Analysis
Technical Summary
Socket.IO versions >=6.5.0 and <6.6.7 with WebTransport enabled in Engine.IO servers improperly handle crafted session IDs like __proto__ by resolving them through inherited properties of the clients object during WebTransport upgrade handling. This leads to a TypeError and causes a denial of service. The vulnerability is classified as CWE-20 (Improper Input Validation). The issue is addressed in version 6.6.7.
Potential Impact
An attacker can cause a denial of service by sending a specially crafted session ID that triggers a TypeError in the server during WebTransport upgrade handling. There is no impact on confidentiality or integrity, but availability is affected due to service disruption.
Mitigation Recommendations
Upgrade socket.io to version 6.6.7 or later where this issue is fixed. Patch status is confirmed by the vendor advisory indicating the fix in 6.6.7. No additional mitigations are specified.
CVE-2026-59724: CWE-20: Improper Input Validation in socketio socket.io
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 v3.1
Score 7.5high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Socket.IO versions >=6.5.0 and <6.6.7 with WebTransport enabled in Engine.IO servers improperly handle crafted session IDs like __proto__ by resolving them through inherited properties of the clients object during WebTransport upgrade handling. This leads to a TypeError and causes a denial of service. The vulnerability is classified as CWE-20 (Improper Input Validation). The issue is addressed in version 6.6.7.
Potential Impact
An attacker can cause a denial of service by sending a specially crafted session ID that triggers a TypeError in the server during WebTransport upgrade handling. There is no impact on confidentiality or integrity, but availability is affected due to service disruption.
Mitigation Recommendations
Upgrade socket.io to version 6.6.7 or later where this issue is fixed. Patch status is confirmed by the vendor advisory indicating the fix in 6.6.7. No additional mitigations are specified.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-07-06T15:34:16.916Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4e73c2c9d9e3dbe36042a5
Added to database: 07/08/2026, 15:58:58 UTC
Last enriched: 07/08/2026, 16:13:43 UTC
Last updated: 07/09/2026, 03:28:10 UTC
Views: 9
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