Authored by houjingyi

VMware ThinApp suffered from a dll hijacking vulnerability.

advisories | CVE-2021-22000

A few months ago I disclosed IBM(R) Db2(R) Windows client DLL
Hijacking Vulnerability(0day) I found:

In that post I mentioned the vulnerability did not get fully patched.

After I told IBM on hackerone that I disclosed it, hackerone asked me
to delete the post, IBM apologized and fully patched the

But this is not the point today. I found a similar problem in

After install the software create C:DummyTLS and rename a dll you
want to load to dummyTLS.dll and put it to C:DummyTLSdummyTLS.dll.

Run "C:Program Files (x86)VMwareVMware ThinAppSetup Capture.exe"
and C:DummyTLSdummyTLS.dll will be loaded.
(other exe like log_monitor.exe/snapshot.exe vulnerable too).

This is also because they use code like:

LoadLibraryExW(L"DummyTLSdummyTLS.dll", 0, 0);

In short, Windows will treat relative path in LoadLibrary(and many
other functions) as the path rooted relative to the current disk

Let us look into code in ntdll.dll. The logic here is:
In LdrpPreprocessDllName after calling
RtlDetermineDosPathNameType_Ustr it will return 4(RtlPathTypeRooted).

And after calling LdrpGetFullPath we get "C:DummyTLSdummyTLS.dll"!

You should not call LoadLibrary with the relative path. In fact, using
relative path is dangerous in many cases.

This was fixed in 2021-07-13 as CVE-2021-22000 and the advisory is
here :

For these vulnerabilities I will post a summary at