Patch Tuesday: Watch Those Evil Web Sites

Microsoft has released nine bulletins today, five of them Critical, four of them Important.  The bulletins cover a gamut of affected products – almost everything in your enterprise will need to be patched today with the exception of Internet Explorer.  No Internet Explorer patches this month!

The majority of bulletin releases these days relate to client-side vulnerabilities – visit an evil website, open an evil document, or read an evil email and you’ll get hacked.  These vulnerabilities are of greatest concern on the desktop where end users are filling time between Mafia Wars power-ups and Facebook updates by visiting websites that may be hosting content of questionable repute.  This month, there are five bulletins addressing these types of issues.

The remaining four bulletins address server-side vulnerabilities.  These are the ones that keep network administrators up at night.  The attacker simply needs network access to the system in question and they can run code of their choice on the server.  This month, there is one flaw that lets anyone with network access own a WINS server, two flaws that let authenticated users own any system, and one flaw that let’s unauthenticated users create a denial of service against some IIS7 web servers.

I always encourage patching the server-side issues as soon as possible.  Maybe best to form two teams and patch server-side and client-side issues simultaneously.

The Bulletins

Now, on to the bulletins.  Starting with the more interesting ones…

MS09-036 is a bulletin that will impact folks running websites on IIS7.  Attackers can send some packets to your web server and cause it to stop functioning (Denial of Service).  Microsoft has already had some reports that this attack has been spotted on the Internet.  IIS7 websites are safe if they are running in ‘Classic’ mode.  IIS7 sites running in ‘Integrated’ (non-classic) mode are vulnerable.  I’m not exactly sure what the default mode is when setting up an IIS7 website.  The patch for this IIS issue is really a patch .Net Framework versions 2 and 3.  If you’re running IIS7 (classic or otherwise), I’d recommend patching this one soon, unless you want your .asp and .aspx pages to stop functioning.

MS09-037 is a really ugly collection of ActiveX controls that have been patched for the ATL vulnerabilities described in the out of band bulletin MS09-035 from earlier this month.  Microsoft identified 5 ActiveX controls that were using a vulnerable version of the ATL templates.  These ActiveX controls could be executed when visiting evil websites – causing them to execute evil code on your system.  Although Microsoft references a Video Control fix in this bulletin, this is NOT the same ActiveX control that was kill-bitted in MS09-032.

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MS09-042 is a Telnet bulletin that is really a throwback to the credential reflection vulnerabilities discussed in MS08-068 (and originally identified back in 201).  This is a variant on the http attack vector discussed in MS08-068.  In this instance, the attacker encourages a user to click on a hyperlink where the link is an evil Telnet server.  The evil Telnet server obtains a form of your Windows username and password – they can replay this set of credentials back against your box to login to your system as you – without every knowing your password!  This attack has been publicly known for a long time – so best to patch all of your desktops for this issue before the bad guys start standing up evil Telnet servers. (you may be safe from this attack if you’re on a corporate network that’s blocking inbound NetBIOS ports 139 and 445 – as those are the ports the attacker will most likely try and use to login to your system with the captured credentials).  See for more information on credential reflection attacks.

MS09-039 is a Critical issue for network administrators managing WINS servers on their Microsoft networks (and every MS network has at least one of these).  This is an unauthenticated server-side attack – the bad guy simply points and shoots some packets at the WINS server and they can execute code of their choice on that server.  This attack is most likely to come from inside your network as the necessary ports to execute the attack are usually blocked at the Internet firewall.  Patch this right away on your WINS servers.

Speaking of the internal network, MS09-041 can be enjoyed internally.  This is a privilege escalation attack against Microsoft systems.  Attackers who have user-level access to machines in the organization (their own machine, file servers, domain controllers, etc) can point some evil packets to their target of choice and execute code.  This vulnerability results from a flaw in the ‘Workstation’ service which is on every machine (and can’t really be disabled without impacting operations on the network).  Patch this one while patching your WINS servers – keep idle internal miscreants from owning your machines.

A less prevalent attack surface in MS09-040 – similar to 09-041 above – but limited to those systems who have installed the MSMQ services (not installed by default).  Attacker can point and shoot packets at the MSMQ service and execute code of their choice.  Like with 09-041, the attacker needs to have valid credentials to the system they’d like to own.

MS09-044 is the last super interesting bulletin this month.  Vulnerabilities in the Remote Desktop Protocol (RDP – formerly known as Terminal Services) can allow attackers to execute code on your desktop should you visit their evil website or visit their evil TermServer.  Two flaws exist, one in the TermServices ActiveX control (which can be launched by visiting an evil website), and one in the RDP console application.  Using the RDP console and visiting an evil TermServer can let the attacker run code on your box.  It’s not a vulnerability in Terminal Services – your remote servers that you access via RDP are safe.  It’s a vulnerability in the client you use to access terminal services.  Patch this one before you go browsing around to evil websites (or trying to break into unknown Terminal Servers).

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The last few issues include a bulletin for Office Web Components (09-043) that were being actively exploited since June (visit the evil website and get hacked), and a bulletin for Windows Media Player (MS09-038) where visiting an evil website hosting malformed AVI files could execute code on your system.

Eric Schultze

About Eric Schultze

Eric Schultze manages Shavlik's product vision and implementation. Schultze most recently served as a program manager for the Microsoft Security Response Center and a senior technologist in the Trustworthy Computing team at Microsoft Corporation. In those roles he managed the Microsoft security patch and bulletin release process and developed security solutions for Microsoft products including patch management and deployment solutions. Before joining Microsoft, Schultze co-founded Foundstone, Inc., where he directed their "Ultimate Hacking: Hands On" training program. His experiences in assessing, penetrating, and securing Microsoft technologies formed the basis of Foundstone's audit and assessment methodologies for Windows operating systems. Prior to starting Foundstone, Schultze was a senior manager in Ernst & Young's national Attack & Penetration group, where he was widely recognized as the firm's expert on Microsoft security. Eric has Bachelor of Arts degrees in Psychology and Sociology from Amherst College.

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