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.
The default servlet (org.apache.catalina.servlets.DefaultServlet) in Tomcat 4.0.4 and 4.1.10 and earlier allows remote attackers to read source code for server files via a direct request to the servlet.