java/org/apache/catalina/authenticator/FormAuthenticator.java in the form authentication feature in Apache Tomcat 6.0.21 through 6.0.36 and 7.x before 7.0.33 does not properly handle the relationships between authentication requirements and sessions, which allows remote attackers to inject a request into a session by sending this request during completion of the login form, a variant of a session fixation attack.