Apache Subversion's mod_dontdothat module and HTTP clients 1.4.0 through 1.8.16, and 1.9.0 through 1.9.4 are vulnerable to a denial-of-service attack caused by exponential XML entity expansion. The attack can cause the targeted process to consume an excessive amount of CPU resources or memory.
https://www.oracle.com/security-alerts/cpuoct2020.html
https://subversion.apache.org/security/CVE-2016-8734-advisory.txt
http://www.securitytracker.com/id/1037361