The present embodiments provide methods for detecting errors and vulnerabilities in software without access to its source code. The method entails extracting functions from dynamically linked applications, determining error return codes and error numbers for the extracted functions, and forming a wrapper using the extracted functions. The wrapper is used to intercept some of the function calls, wherein the intercepted functions are manipulated to fail. The embodiments further relate to an article of manufacture to detect errors. The article of manufacture utilizes an extraction module to extract functions from dynamically linked applications, software to compile error return codes and error numbers for functions, and a wrapper module to form a wrapper with the extracted functions.