SV.DLLPRELOAD.NONABSOLUTE.DLLPotential DLL-preload hijack vectorWhen an application loads an external library, it's important for the code to use a fully qualified path. If an insufficiently qualified path is specified, a malicious attacker can gain control of the search path and use it as a vector for remotely executing arbitrary code. This type of threat is known as binary planting or DLL-preloading attacks. The DLLPRELOAD.NONABSOLUTE.DLL checker flags code instances in which there are missing or NULL pathnames in system file-manipulation function calls LoadLibrary and LoadLibraryEx to .dll files. Fore more information on DLL-preloading attacks, see Microsoft's Security Advisory 2269637. Vulnerability and riskAn attacker can use relative pathnames to read, modify, or overwrite critical files, bypassing security mechanisms. Failure to use a fully qualified path can allow your application to load a DLL other than that intended. An exploiter can use this vulnerability to gain user rights, achieve elevated privileges, and even take control of the system. Mitigation and preventionTo avoid relative path problems:
For more suggestions for mitigation and prevention of DLL-preloading attacks, see Microsoft's Dynamic-Link Library Security article. Vulnerable code example
1 HINSTANCE myLoadLibraryX() {
2 return LoadLibrary("X.dll");
3 }
Klocwork produces an issue report at line 2 indicating that calling LoadLibrary without a fully qualified path may allow the application to load a DLL from an arbitrary location. Any call to a file-manipulation function that uses a relative or NULL pathname can produce an unpredictable and possibly dangerous response. Fixed code example
1 HINSTANCE myLoadLibraryX() {
2 return LoadLibrary("C:\\myapp\\X.dll");
3 }
In the fixed code example, a fully qualified path has been provided, eliminating the possibility of malicious access. Related checkersExternal guidance
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