# CVE-2026-102600: Socket.IO cluster-engine prototype pollution denial of service

Source: https://junglewise.ai/threats/cve-2026-102600-socket-io-enables-bidirectional-and-low-latency-communication  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-29. Updated: 2026-09-29  
License: CC BY 4.0 with a link back

CVE-2026-102600 · Severity: high · CVSS 7.5 · Published 2026-09-29

Socket.IO cluster-engine is a library that enables real-time communication in distributed Node.js applications. The library is vulnerable to a prototype pollution attack where specially crafted session IDs can crash the Node.js process, causing service outages. Applications not using the cluster-engine component are unaffected, and the issue is fixed in version 0.1.1.

Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [Socket.IO](https://junglewise.ai/threats/vendors/socket-io).

## Quick answers

**Is CVE-2026-102600 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102600 being exploited in the wild.

**How severe is CVE-2026-102600?** High severity, with a CVSS score of 7.5, published 29 September 2026.

**Which products and versions are affected?** @socket.io/cluster-engine (npm) < 0.1.1, SEMVER:introduced=0,fixed=0.1.1; Socket.IO Cluster-Engine prior to 0.1.1.

**Is there a fix for CVE-2026-102600?** Yes. @socket.io/cluster-engine (npm): upgrade to 0.1.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-102600 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-102600?** Check whether you run @socket.io/cluster-engine (npm) or Socket.IO Cluster-Engine at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @socket.io/cluster-engine (npm): upgrade to 0.1.1 or later

  ```sh
  npm install @socket.io/cluster-engine@0.1.1
  ```


## Technical details

The vulnerability exists in @socket.io/cluster-engine versions prior to 0.1.1, where session ID lookups directly access object properties without sanitization, allowing attacker-controlled input like __proto__ or constructor to traverse the prototype chain. The attack requires network access to send malicious session IDs in a clustered deployment, triggering a Node.js process crash. The fix guards client lookups against prototype pollution in version 0.1.1.

## Affected products

- Socket.IO cluster-engine prior to 0.1.1

## Identifiers

- CVE-2026-102600
- GHSA-wfpm-5gcm-94cg

## Timeline

- 2026-09-29: disclosed
- 2026-09-08: patched: version 0.1.1 released

## References

- [https://github.com/socketio/socket.io/commit/830e3642ebb8dc3784eb749b0a004fe2b932b429](https://github.com/socketio/socket.io/commit/830e3642ebb8dc3784eb749b0a004fe2b932b429)
- [https://github.com/socketio/socket.io/releases/tag/@socket.io/cluster-engine@0.1.1](https://github.com/socketio/socket.io/releases/tag/@socket.io/cluster-engine@0.1.1)