CVE-2012-5370 jruby: Murmur hash function collisions (oCERT-2012-001)

JRuby computes hash values without properly 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, as demonstrated by a universal multicollision attack
against the MurmurHash2 algorithm, a different vulnerability than CVE-2011-4838.