VMware ThinApp DLL Hijacking

CVE Category Price Severity
CVE-2021-22000 CWE-426 $5,000 High
Author Risk Exploitation Type Date
Cem Onat Karagun High Local 2021-07-16
CVSS:4.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H 0.02192 0.50148

CVSS vector description

Our sensors found this exploit at:

Below is a copy:

VMware ThinApp DLL Hijacking
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:\DummyTLS\dummyTLS.dll.

Run "C:\Program Files (x86)\VMware\VMware ThinApp\Setup Capture.exe"
and C:\DummyTLS\dummyTLS.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:\DummyTLS\dummyTLS.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

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