High 7.5Published Sep 29, 2026

CVE-2026-102600Socket.IO: Prototype Pollution via Unsafe Client Session Lookup

Updated under an hour ago (2026-10-19 07:30 UTC)

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It affects socketio socket.io and 1 other product. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.37%, higher than 29% of scored CVEs.

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Every CVE for socketio socket.io

Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-20, CWE-1321
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.37% (percentile 29)
Assigned by: GitHub_M
NVD analysis: Awaiting Analysis
Record last updated: Sep 29, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

socketio socket.io socketio:socket.io (from the name)	before 0.1.1	CNA record
@socket.io cluster-engine socket.io:cluster_engine (from the name)	before 0.1.1	CNA record

References

https://github.com/socketio/socket.io/security/advisories/GHSA-wfpm-5gcm-94cgx-refsource-confirm
https://github.com/socketio/socket.io/commit/830e3642ebb8dc3784eb749b0a004fe2b932b429x-refsource-misc
https://github.com/socketio/socket.io/releases/tag/@socket.io/cluster-engine@0.1.1x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.