In Apache PDFBox 1.8.0 to 1.8.15 and 2.0.0RC1 to 2.0.11, a carefully crafted PDF file can trigger an extremely long running computation when parsing the page tree.
https://www.oracle.com/security-alerts/cpuapr2020.html
https://lists.debian.org/debian-lts-announce/2018/10/msg00008.html