The crack gem 0.3.1 and earlier for Ruby does not properly restrict casts of string values, which might allow remote attackers to conduct object-injection attacks and execute arbitrary code, or cause a denial of service (memory and CPU consumption) by leveraging Action Pack support for (1) YAML type conversion or (2) Symbol type conversion, a similar vulnerability to CVE-2013-0156.
Gentoo Linux Security Advisory 201404-4 - A vulnerability in Crack might allow remote attackers to execute arbitrary code. Versions less than 0.3.2 are affected.