The mod_dav_svn Apache HTTPD server module in Subversion 1.6.0 through 1.6.20 and 1.7.0 through 1.7.8 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via an anonymous LOCK for a URL that does not exist.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A18538
https://bugzilla.redhat.com/show_bug.cgi?id=929090
http://www.ubuntu.com/usn/USN-1893-1
http://www.mandriva.com/security/advisories?name=MDVSA-2013:153
http://subversion.apache.org/security/CVE-2013-1847-advisory.txt
http://rhn.redhat.com/errata/RHSA-2013-0737.html
http://lists.opensuse.org/opensuse-updates/2013-06/msg00069.html
http://lists.opensuse.org/opensuse-updates/2013-04/msg00095.html