active_support/core_ext/hash/conversions.rb in Ruby on Rails before 2.3.15, 3.0.x before 3.0.19, 3.1.x before 3.1.10, and 3.2.x before 3.2.11 does not properly restrict casts of string values, which allows remote attackers to conduct object-injection attacks and execute arbitrary code, or cause a denial of service (memory and CPU consumption) involving nested XML entity references, by leveraging Action Pack support for (1) YAML type conversion or (2) Symbol type conversion.
