Oracle Java SE before 7 Update 6, and OpenJDK 7 before 7u6 build 12 and 8 before build 39, computes hash values without restricting the ability to trigger hash collisions predictably, which allows context-dependent attackers to cause a denial of service (CPU consumption) via crafted input to an application that maintains a hash table.
https://bugzilla.redhat.com/show_bug.cgi?id=750533
http://www.openwall.com/lists/oss-security/2012/06/17/1
http://www.openwall.com/lists/oss-security/2012/06/15/12
http://www.ocert.org/advisories/ocert-2011-003.html
http://www.nruns.com/_downloads/advisory28122011.pdf
http://www.kb.cert.org/vuls/id/903934
http://mail.openjdk.java.net/pipermail/core-libs-dev/2012-May/010238.html