Jakarta Tomcat 5.0.19 (Coyote/1.1) and Tomcat 4.1.24 (Coyote/1.0) allows remote attackers to poison the web cache, bypass web application firewall protection, and conduct XSS attacks via an HTTP request with both a "Transfer-Encoding: chunked" header and a Content-Length header, which causes Tomcat to incorrectly handle and forward the body of the request in a way that causes the receiving server to process it as a separate HTTP request, aka "HTTP Request Smuggling."

Tomcat 4.0 through 4.1.12, using mod_jk 1.2.1 module on Apache 1.3 through 1.3.27, allows remote attackers to cause a denial of service (desynchronized communications) via an HTTP GET request with a Transfer-Encoding chunked field with invalid values.