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25 October 2026

advisoryOfficial CVE List25 Oct 2026

Socket.IO: Engine.IO Protocol Revision Mismatch DoS

Socket.IO enables bidirectional and low-latency communication for every platform. From Engine.IO 6.6.0 until 6.6.10, a transport upgrade can independently derive an Engine.IO protocol revision from the upgrade request instead of enforcing the revision stored on the existing session. A malicious client can establish a valid session and send an upgrade request with a different or omitted EIO query parameter, attaching a transport with incompatible parser and heartbeat behavior. A crafted heartbeat packet can then trigger an uncaught exception and terminate the Node.js process, including when Engine.IO v3 compatibility is disabled because an omitted EIO value is interpreted as revision 3 on the affected path. This issue is fixed in Engine.IO 6.6.10.

socket.io CVE-2026-102599

Structured advisory · Revision 1Original source

Evidence and details

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-102599

socket.io

Source reference: /containers/cna/affected/0/product

Affected versions: Not stated in this record
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

Related CVEs: CVE-2026-102599
Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event: #34512 · Revision 1
Added to Heist Feed: Sun, 25 Oct 2026 09:24:19 GMT
Publisher date: Tue, 13 Oct 2026 19:05:10 GMT

Read the original announcement

24 October 2026

advisoryOfficial CVE List24 Oct 2026

Socket.IO: Prototype Pollution via Unsafe Client Session Lookup

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.

socket.io cluster-engine CVE-2026-102600