It was reported that Jetty path normalization mechanism implemented in PathResource class and introduced in Jetty versions 9.3.x is vulnerable to malicious URL requests containing specific escaped characters. Malicious user can gain access to protected resources (e.g. WEB-INF and META-INF folders and their contents) and defeat application filters or other security constraints implemented in the servlet configuration.

For mitigation, see external reference.

External Reference:

http://www.ocert.org/advisories/ocert-2016-001.html