This is a followup to <http://seclists.org/fulldisclosure/2012/Mar/17> and <http://seclists.org/fulldisclosure/2013/Aug/225>: On Sunday, March 04, 2012 9:06 PM I wrote: > Hi @ll, > > the system image "\Setup\WIM\setup.wim" on the "POSReady 2009 eval CD", > available from the Microsoft Download Center under > <http://www.microsoft.com/downloads/en/details.aspx?FamilyID=1e077ece-3f19-4c41-b219-6fcc821fb5fc>, > contains the following registry entries: > > [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\SSOExec] > "Asynchronous"=dword:00000001 > "Impersonate"=dword:00000001 > "Logoff"="SSOReset" > "Unlock"="SSOExec" > "Lock"="SSOReset" > "DLLName"="%windir%\\temp\\sso\\ssoexec.dll" [...] > To complete the picture: the ACLs on the directory "%windir%\temp" in > systems installed from this image/CD allow unprivileged users to create > a subdirectory "sso" in "%windir%\temp" and then the "ssoexec.dll", > allowing them to have their code run under every (other) user account > used to log on afterwards, resulting in a privilege escalation. After I learned that the same vulnerability exists in EVERY installation of Windows Embedded POSReady 2009 I contacted a vendor and Microsoft again. The vendor got the following reply from Microsoft: | The Microsoft Windows Embedded Product team, along with the MSRC | (Microsoft Security Response Center) team researched this in early | 2012 and determined that this is a not a vulnerability because ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | Microsoft Malware Protection Center does not consider this to be ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | malware. ~~~~~~~~ OUCH! How absurd! | It was determined that these keys came from XP Embedded and | the Standard Windows Logon Component. They found no evidence of | malware on our build systems and the presence of the keys is not | an indication that malware was ever present on the systems There is no file "ssoexec.dll" in Windows Embedded POSReady 2009! As far as I know there is no file by this name in ANY version/variant of Windows! I requested clarification about these absurd statements and whether a hotfix will be provided from the MSRC <secure@xxxxxxxxxxxxx> and got the following answer: | Could you explain how the EOP attack works using this DLL? | Normal users don't have write permission to %windir%, and if an | attacker controls an Administrator account then they've already | defeated security. to which I replied: | The directory in question is but "%windir%\temp\"! | In Windows Embedded POSReady 2009 UNPRIVILEGED users can create | the subdirectory "sso\" and the DLL "ssoexec.dll". | Game over! which yield another absurd answer from the MSRC: | After some research, it appears this EOP attack requires that the | attacker has already violated one of the 10 Immutable Laws of Security | (http://technet.microsoft.com/library/cc722487.aspx ), most notably | laws #1 or #3. You should read the article to understand why those | laws matter. OUCH! I asked the MSRC again: | which part of "In Windows Embedded POSReady 2009 UNPRIVILEGED users | can create the subdirectory "sso\" and the DLL "ssoexec.dll" is not | understood? and got the final answer: | We are aware of the issues and arguments you've mentioned. An attacker | in a position to carry out these attacks could also carry out many | other attacks we can't stop. The link provided below explains this in | detail. OUCH! Stefan Kanthak
