Impact Twisted Web is vulnerable to request smuggling attacks: 1. "When presented with two content-length headers, Twisted Web ignored the first header. When the second content-length was set to zero this caused Twisted Web to interpret the request body as a pipelined request. According to RFC 7230 Section 3.3.3#4, if a message is received with multiple content-length headers with differing value, then the server must reject the message with a 400 response." (Jake Miller of Bishop Fox Security) 2. " When presented with a content-length and a chunked encoding header, the content-length took precedence and the remainder of the request body was interpreted by Twisted Web as a pipelined request. According to RFC 7230 Section 3.3.3#3, if a message with both content-length and chunked encoding is accepted, transfer-encoding overrides the content-length." (Jake Miller of Bishop Fox Security) 3. ~"Twisted should not allow BWS between the filed-name and colon." (ZeddYu Lu)~ closed in 9646 4. "Two CL header with different values is also not allowed." (ZeddYu Lu) 5. "Only accept identity and chunked Transport-Encoding." (ZeddYu Lu) Patches https://github.com/twisted/twisted/commit/20c787a14a09e7cbd5dfd8df08ceff00d1fcc081 https://github.com/twisted/twisted/commit/4a7d22e490bb8ff836892cc99a1f54b85ccb0281 Workarounds N/A References https://portswigger.net/web-security/request-smuggling