Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, 6.0.0 through 6.0.18, and possibly earlier versions normalizes the target pathname before filtering the query string when using the RequestDispatcher method, which allows remote attackers to bypass intended access restrictions and conduct directory traversal attacks via .. (dot dot) sequences and the WEB-INF directory in a Request.
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.