If Apache Tomcat 8.5.0 to 8.5.82, 9.0.0-M1 to 9.0.67, 10.0.0-M1 to 10.0.26 or 10.1.0-M1 to 10.1.0 was configured to ignore invalid HTTP headers via setting rejectIllegalHeader to false (the default for 8.5.x only), Tomcat did not reject a request containing an invalid Content-Length header making a request smuggling attack possible if Tomcat was located behind a reverse proxy that also failed to reject the request with the invalid header.
Exploitability
AV:NAC:LPR:NUI:NScope
S:UImpact
C:NI:HA:N7.5/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:NOther