The socket.io-parser npm package before versions 3.3.2 and 3.4.1 allows attackers to cause a denial of service (memory consumption) via a large packet because a concatenation approach is used.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-36049
• socketio/socket.io-parser@dcb942d
• https://blog.caller.xyz/socketio-engineio-dos/
• https://github.com/bcaller/kill-engine-io
• https://github.com/socketio/socket.io-parser/releases/tag/3.3.2
• https://github.com/socketio/socket.io-parser/releases/tag/3.4.1
• https://www.npmjs.com/package/socket.io-parser