https://bugzilla.redhat.com/show_bug.cgi?id=1806835
--- Doc Text *updated* by Ted (Jong Seok) Won jwon@redhat.com --- The HTTP header parsing code used an approach to end-of-line (EOL) parsing that allowed some invalid HTTP headers to be parsed as valid. This led to a possibility of HTTP Request Smuggling if Tomcat was located behind a reverse proxy that incorrectly handled the invalid Transfer-Encoding header in a particular manner. Such a reverse proxy is considered unlikely.
It affects the version of Apache Tomcat 9 from 9.0.0.M1 to 9.0.30, Tomcat from 8 8.5.0 to 8.5.50, and Tomcat 7 7.0.0 to 7.0.99.