It was found that URLResource.getLastModified() in Undertow closes the file descriptors only when they are finalized which can cause file descriptors to exhaust. This leads to a file handler leak.
https://issues.jboss.org/browse/UNDERTOW-1338
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-1114
https://bugs.openjdk.java.net/browse/JDK-6956385
https://access.redhat.com/errata/RHSA-2019:0877