The URLValidator class in Apache Struts 2 2.3.20 through 2.3.28.1 and 2.5.x before 2.5.1 allows remote attackers to cause a denial of service via a null value for a URL field.
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2016-4465.json"