Ruby (aka CRuby) 1.9 before 1.9.3-p327 and 2.0 before r37575 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 a variant of the MurmurHash2
algorithm, a different vulnerability than CVE-2011-4815.