Reflections on July 2009 Patch Day

6 security bulletins released today – 3 Critical and 3 Important. Two of the issues are being actively exploited on the Internet and four of the issues are client-side vulnerabilities, which means the exploit can only occur if a user visits an evil website or opens a malformed document.

Today’s release is important because patches were released for two recent 0-day attacks – a QuickTime file parsing vulnerability and the recently announced Directshow vulnerability. Both vulnerabilities are reported as being actively exploited on the Internet.

While Microsoft has announced workarounds and/or provided Fixit tools for each of these issues, today’s patches will be welcomed by network administrators who have been tasked with remediating these issues. Shavlik recommends that network administrators download and install the patches for these two bulletins as soon as possible (MS09-032 and MS09-028)

Two of Microsoft’s other releases this month apply to products that you don’t see patched very often – ISA Server 2006 and Virtual PC. Although these two products are associated with security functions, neither flaw is as bad as it seems and Microsoft has rated the severity for each of these as Important.

Of the two remaining bulletins, one applies to Publisher (Important) and one applies to the Operating System (Critical). Neither of these issues were publicly known prior to release, though Shavlik recommends reviewing and installing each of these patches as appropriate on your networks. The Operating System patch (MS09-029) is particularly nasty and can execute when a user views an evil web page, email, or Office document.

Shavlik recommends installing MS09-028, 29, and 32 patches first (DirectShow, OS Font patch, and Video Control). These are the three Critical patches – which goes to show that Microsoft got the Severity ratings spot-on this month.

Details for MS09-032 and MS09-028:
MS09-032 is the bulletin for the QuickTime file parsing vulnerability. Clicking on an evil hyperlink or even hovering your mouse over a malformed QuickTime file could allow the attacker to execute code on your system. The attacker’s code would have the same level of permission to your computer as the person who is logged on to the computer. If you’re logged on as admin, the exploit could add or remove users and administrators from your machine, delete files, reformat your hard drive, or embed trojans or worms that could be used in future attacks.

It’s important to note for this issue that the presence or absence of Apple QuickTime is not relevant to whether or not your computer is vulnerable to this issue. The flaw resides in the Microsoft components that parse QuickTime files – so don’t believe that you’re safe just because you don’t have QuickTime installed. Also, the recent QuickTime patch from Apple (7.6.2) is not related to this issue.

MS09-032 is rated as Critical for all Operating Systems.

MS09-028 is the bulletin for the recently announced Microsoft DirectShow vulnerability. Viewing a malformed media file from a Windows XP or Windows Server 2003 system can enable the attacker to execute code on your system. Similar to MS09-032, the evil code will run in the context of the currently logged on user and can take any action on that system that the logged on user can take.

Microsoft released a FixIt tool that sets the browser killbits for this vulnerable section of code. The MS09-032 patch is a cumulative killbit patch that includes the killbits from the FixIt tool as well as all previously released ActiveX killbits. Users who installed the ActiveX cumulative patch from June 2009 and also ran the FixIt tool for the DirectShow have already implemented the complete set of killbits reprented by the MS09-028 patch. If you ran the FixIt tool or otherwise implemented the Microsoft suggested workaround you are safe – there’s no need to revert changes that you made.

While the public exploit only impacts XP and 2003 systems, Microsoft recommends installing this patch on all Operating Systems as it includes killbits for all previously known bad ActiveX controls.

Details for the remaining four:
MS09-029 applies to all Operating Systems and could be a particularly nasty issue if left unpatched. The flaw resides in the way that Microsoft parses embedded fonts on web pages, emails, and Office documents. (in this case, embedded opentype fonts. EOT fonts ensure that everyone viewing the text sees it formatted the same way.) Viewing an evil web page, email, or Office doc could allow the attacker to execute code on your system. Workarounds are available, but it requires two separate changes to be made – one to protect from web content and the other to protect from evil emails and documents.

MS09-030 is a vulnerability in Microsoft Publisher documents. Viewing a malformed document could allow the attacker to run code on your system. This seems like the hundredth vulnerability in Publisher this year, and the millionth ‘open an evil document and get hacked’ vulnerability in the past two years.

MS09-031 discusses an issue with ISA Server 2006. If the ISA Server is specifically configured to use Radius one-time-passwords AND to use Kerberos for authentication AND to fallback to basic http authentication when asked, the attacker may be able to access servers protected by the firewall if they know the username of those target systems. It sounds scary, but it’s probably a very small number of systems in the world that are configured exactly this way. An edge case at best. If you have an ISA Server 2006 and you’re concerned that you might meet all three criteria above, it’s best to patch your system.

MS09-033 relates to Guest Operating Systems that are hosted on Microsoft Virtual PC or Virtual Server. These virtualized systems are subject to a privilege escalation attack. (Non-virtualized systems are not vulnerable.) Users who can execute code on the virtual systems can run an exploit and become administrator on the virtual images. At no time can this flaw lead to compromise of the underlying Virtual PC or Virtual Server. IOW, it’s not the much-hyped but yet-to-be-seen exploit that crosses the virtualization barrier.


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