CVE-2026-102600 Socket.IO: Prototype Pollution via Unsafe Client Session Lookup
Attacker can crash Node.js process via prototype pollution in clustered Socket.IO deployments, causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-102600?
CVE-2026-102600 is a high-severity vulnerability in @socket.io cluster-engine, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-102600?
2 open source packages ship an affected version, including @socket.io/cluster-engine.
| Package | Affected | Fixed in |
|---|---|---|
@socket.io/cluster-engine npm | All versions | 0.1.1 |
@socket.io/cluster-engine npm | All versions | 0.1.1 |
How do I fix CVE-2026-102600?
Upgrade @socket.io/cluster-engine to 0.1.1 or later.
Is CVE-2026-102600 being exploited?
There is no known exploitation of CVE-2026-102600 in the wild and no public exploit code.
Sources
Also known as GHSA-wfpm-5gcm-94cg.