The team has identified a critical vulnerability in the http server of the most recent version of Node, where malformed headers can lead to HTTP request smuggling. Specifically, if a space is placed before a content-length header, it is not interpreted correctly, enabling attackers to smuggle in a second request within the body of the first.

An attacker can make the Node.js HTTP/2 server completely unavailable by sending a small amount of HTTP/2 frames packets with a few HTTP/2 frames inside. It is possible to leave some data in nghttp2 memory after reset when headers with HTTP/2 CONTINUATION frame are sent to the server and then a TCP connection is abruptly closed by the client triggering the Http2Session destructor while header frames are still being processed (and stored in memory) causing a race condition.