CVE-2026-102600

Socket.IO: Prototype Pollution via Unsafe Client Session Lookup

State: Published
Severity: 7.5 High
Published: Sep 29, 2026
Updated: Sep 29, 2026
Reserved: Sep 29, 2026

Description

Socket.IO enables bidirectional and low-latency communication for every platform. Prior to 0.1.1, @socket.io/cluster-engine uses inherited object properties when looking up attacker-controlled session IDs in clustered deployments. Special property names such as __proto__ or constructor can resolve through the object prototype chain instead of identifying an actual connected client, causing the Node.js process to crash and resulting in denial of service. Applications that do not use @socket.io/cluster-engine are not affected. This issue is fixed in version 0.1.1.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	GitHub_M

Weaknesses

CWE-20 Improper Input Validation
CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Affected Products

Product	Versions
socket.iosocketio	< 0.1.1Affected
cluster-engine@socket.io	< 0.1.1Affected

References

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