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Windows Authentication UI DLL side loading vulnerability
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Yorick Koster, August 2015

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Abstract
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A DLL side loading vulnerability was found in the Windows Authentication
UI DLL. This issue can be exploited by loading the Slide To Shut Down
Screen object as an embedded OLE object. When instantiating the object
Windows will try to load the DLL wuaext.dll from the current working
directory. If an attacker convinces the user to open a specially crafted
(Office) document from a directory also containing the attacker's DLL
file, it is possible to execute arbitrary code with the privileges of
the target user. This can potentially result in the attacker taking
complete control of the affected system.

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See also
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-6132
https://technet.microsoft.com/library/security/MS15-132
https://advisory.securify.nl/blog/SFY20151201/there_s_a_party_in_ole__and_you_are_invited.html

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Tested versions
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This issue was successfully verified on Windows 10 + Office 2013 32-bit,
and Windows 10 + Office 2016 64-bit.

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Fix
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Microsoft released MS15-132 that fixes this vulnerability.

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Details
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https://www.securify.nl/advisory/SFY20150803/windows_authentication_ui_dll_side_loading_vulnerability.html