full-disclosure - Re: [FD] Defense in depth -- the Microsoft way (part 64): Windows Defender loads and exeutes arbitrary DLLs

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Date: Fri, 27 Mar 2020 23:25:50 +0000
From: Paul Szabo <paul.szabo@...ney.edu.au>
To: Stefan Kanthak <stefan.kanthak@...go.de>, "fulldisclosure@...lists.org"
 <fulldisclosure@...lists.org>
Cc: "bugtraq@...urityfocus.com" <bugtraq@...urityfocus.com>
Subject: Re: [FD] Defense in depth -- the Microsoft way (part 64): Windows
 Defender loads and exeutes arbitrary DLLs

Does this mean that unprivileged users can defeat WindowsDefender,
even when that is "enforced" by managers? Surely that would be a
vulnerability! I am not knowledgeable about Windows management,
but the pages

https://docs.microsoft.com/en-us/configmgr/protect/deploy-use/endpoint-protection

https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-defender-antivirus/configuration-management-reference-windows-defender-antivirus

suggest that enforcement of WindowsDefender is a supported feature.

Thanks, Paul

On 2020-03-27 15:27, Stefan Kanthak wrote:
> in September 2017, Microsoft relocated many executable files of Windows
> Defender from the directory "%ProgramFiles%\Windows Defender\" to
> "%ProgramData%\Microsoft\Windows Defender\platform\<version>\" ...
> Of special interest here is the IOfficeAntiVirus implementation ...
> This interface is called by the attachment manager ...
> "Thanks" to the environment variable specified in the registered path
> "%ProgramData%\Microsoft\Windows Defender\platform\<version>\MpOav.dll",
> an unprivileged user/attacker can provide an arbitrary DLL which is
> then loaded and executed ...
> ...
> Vendor statement:
> The MSRC assigned case 57439 to the above report, and replied with the
> following statements:
> | After investigation, our engineers have determine this this behavior
> | is by-design and does not constitute as a vulnerability as reported.
> ...

-- 
Paul Szabo       psz@...hs.usyd.edu.au       www.maths.usyd.edu.au/u/psz
School of Mathematics and Statistics   University of Sydney    Australia

I support NTEU members taking a stand for workplace rights in the face of
poorly-run change management. Visit www.nteu.org.au/sydney to learn more.

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