VMware ThinApp DLL hijacking vulnerability

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VMware ThinApp DLL hijacking vulnerability

From: houjingyi <houjingyi647 () gmail com>
Date: Wed, 14 Jul 2021 11:35:13 +0800

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"\DummyTLS\dummyTLS.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 : https://www.vmware.com/security/advisories/VMSA-2021-0015.html.

For these vulnerabilities I will post a summary at https://houjingyi233.com.

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