NHibernate is an object-relational mapper for the .NET framework. A SQL injection vulnerability exists in some types implementing ILiteralType.ObjectToSQLString. Callers of these methods are exposed to the vulnerability, which includes mappings using inheritance with discriminator values; HQL queries referencing a static field of the application; users of the SqlInsertBuilder and SqlUpdateBuilder utilities, calling their AddColumn overload taking a literal value; and any direct use of the ObjectToSQLString methods for building SQL queries on the user side. This vulnerability is fixed in 5.4.9 and 5.5.2.