java/org/apache/coyote/ajp/AbstractAjpProcessor.java in Apache Tomcat 8.x before 8.0.4 allows remote attackers to cause a denial of service (thread consumption) by using a "Content-Length: 0" AJP request to trigger a hang in request processing.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.