title: Uncaught Exception in engine.io
description: Engine.IO is the implementation of transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO. A specially crafted HTTP request can trigger an uncaught exception on the Engine.IO server, thus killing the Node.js process. This impacts all the users of the `engine.io` package starting from version `4.0.0`, including those who uses depending packages like `socket.io`. Versions prior to `4.0.0` are not impacted. A fix has been released for each major branch, namely `4.1.2` for the `4.x.x` branch, `5.2.1` for the `5.x.x` branch, and `6.1.1` for the `6.x.x` branch. There is no known workaround except upgrading to a safe version.
problem types: CWE-754: Improper Check for Unusual or Exceptional Conditions
affected:
{
product: engine.io
vendor: socketio
versions:
status: affected, version: >= 4.0.0, < 4.1.2
status: affected, version: >= 5.0.0, < 5.2.1
status: affected, version: >= 6.0.0, < 6.1.1
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.1
]