In Apache Tomcat 9.0.0.M1 to 9.0.30, 8.5.0 to 8.5.50 and 7.0.0 to 7.0.99 the HTTP header parsing code used an approach to end-of-line 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.
https://www.oracle.com/security-alerts/cpuoct2020.html
https://www.oracle.com/security-alerts/cpujul2020.html
https://www.oracle.com/security-alerts/cpujan2021.html
https://www.debian.org/security/2020/dsa-4680
https://www.debian.org/security/2020/dsa-4673
https://usn.ubuntu.com/4448-1/
https://security.netapp.com/advisory/ntap-20200327-0005/
https://lists.debian.org/debian-lts-announce/2020/05/msg00026.html
https://lists.debian.org/debian-lts-announce/2020/03/msg00006.html
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00025.html