In keeping up with the latest releases of Subversion, we rolled out SVN 1.6.4 on all our servers last week. The latest version fixes critical security flaws that include the possibility of DoS attacks (tested) or remote arbitrary code execution.
Subversion servers and clients from version 1.5.6 and later (up to 1.6.3.) are known to be vulnerable to these security flaws. Learn more from the official SVN upgrade notes.