The BigDecimal library in Ruby 1.8.6 before p369 and 1.8.7 before p173 allows context-dependent attackers to cause a denial of service (application crash) via a string argument that represents a large number, as demonstrated by an attempted conversion to the Float data type.

More... (http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2009-1904)