CVE-2019-16785

An HTTP-request vulnerability was discovered in Waitress which implemented a “MAY” part of the RFC7230 which states: “Although the line terminator for the start-line and header fields is the sequence CRLF, a recipient MAY recognize a single LF as a line terminator and ignore any preceding CR.” Unfortunately, if a front-end server does not process header fields with an LF the same way as it processes those with a CRLF, it can lead to the front-end and the back-end server processing the same HTTP message in two different ways. This vulnerability can lead to a potential for HTTP request smuggling and splitting where Waitress may see two requests, while the front-end server only sees a single HTTP message.