MS Patch Tuesday: Exploits expected for severe drive-by-download flaws

Summary:Two of the bulletins are rated "critical" for all versions of Microsoft's flagship operating system, including Windows 7 and Windows Server 2003 R2.

Microsoft today released 11 security bulletins with fixes for a total of 25 security vulnerabilities, including several flaws that expose users to browse-and-you're-hacked (malicious drive-by download) attacks.

Two of the bulletins are rated "critical" for all versions of Microsoft's flagship operating system, including Windows 7 and Windows Server 2003 R2.   In some cases, Microsoft is expecting to see "reliable exploit code" released within 30 days, highlighting the importance of applying these patches immediately.

The company urged its users to pay special attention to three bulletins this month -- MS10-019, MS10-026, and MS10-027.  Here's why:

  • MS10-019 affects all versions of Windows. While we give this a 2 on the exploitability index, the issue would allow an attacker to alter signed executable content (PE and CAB files) without invalidating the signature. Note that WU/MU content is not affected by this issue due to additional checks made when validating signed content.
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  • MS10-026 does not affect Windows 7, Windows Server 2008 R2, or Itanium versions of Windows Server 2008 and Windows Server 2003. However, it is critical on Windows 2000, XP, Server 2003 and Server 2008. The vulnerability could be triggered simply by visiting a web page hosting a specially crafted AVI file that began streaming when the page loads.
  • MS10-027 affects only Windows 2000 and Windows XP users who could potentially be exploited simply by visiting a specially crafted web page.

This chart from Microsoft's SR&D blog provides a great overview of the bulletins, severity risks and mitigations:

Bulletin Most likely attack vector Max Bulletin Severity Max Exploit-ability Index Likely first 30 days impact Platform mitigations and key notes


Victim browses to a malicious webpage. Critical 1 Likely to see reliable exploit code developed Windows Vista, Windows Server 2008, and Windows 7 not affected
MS10-026 (DirectShow) Victim browses to a malicious webpage or opens a malicious AVI movie. Critical 1 Likely to see reliable exploit code developed Windows 7 codec is not vulnerable.
MS10-019 (WinVerifyTrust) Victim double-clicks a malicious EXE or allows malicious content to run because content claims to be signed by a trusted publisher. Critical 2 Likely to see effective proof-of-concept code released to downgrade Authenticode checks from v2 down to v1. Authenticode v1 is a weaker algorithm. To reach code execution, attackers will need to find an Authenticode v1 bypass. Microsoft Update and Windows Update clients not directly vulnerable to this threat.

(SMB Client)

Attacker hosts malicious SMB server within enterprise network. Attacker lures victim to click on a link that causes victim to initiate an SMB connection to the malicious SMB server. Critical 2 Proof-of-concept code already exists for denial-of-service vulnerability. May see unreliable exploit code developed for other client-side SMB vulnerabilities that most often results in denial-of-service. Egress filtering at most corporations will limit exposure to attacker within enterprise network.

Several issues with differing exploitability. Please see SRD blog for more information.



Victim browses to a malicious webpage and is tricked into clicking F1 on a VBScript messagebox. Important 1 Public exploit code exists for code execution after a user presses F1. Have not heard reports of real-world attacks yet, despite public exploit code. Vulnerability not reachable on Windows 7, Windows Server 2008, and Windows Vista by default. Bulletin rated defense-in-depth for those platforms.

Windows Server 2003 not vulnerable by default due to Enhanced Security Configuration.

MS10-025 (Windows Media Services) If a victim Windows 2000 machine has enabled Windows Media Services, an attacker can send network-based attack over port 1755 (TCP or UDP). Critical 1 Likely to see reliable exploit code developed. Only Windows 2000 is affected.


Attacker able to run code locally on a machine exploits a vulnerability to run code at a higher privilege level. Important 1 Likely to see reliable exploit code developed for one or more of these eight vulnerabilities. SRD blog post explaining the Windows registry link vulnerabilities.

(SMTP Service)

Attacker causes SMTP Service running on 64-bit Windows Server 2003 to crash by initiating a DNS lookup handled by a malicious DNS server. Important n/a No chance for code execution. May see proof-of-concept code that crashes SMTP Service but not for Exchange. Exchange Server not directly affected by denial-of-service vulnerability because vulnerable versions never shipped as 64-bit application. Security update applies to 32-bit Exchange Server to add additional DNS protections.


Victim opens malicious .VSD file Important 1 Visio exploits not often seen in the wild. Unsure whether we will see exploit released. Visio not installed by default with most Office installations.


Victim opens malicious .PUB file Important 1 Publisher exploits not often seen in the wild. Unsure whether we will see exploit released.


Attacker spoofs own source address by encapsulating iPv6 attack packet inside IPv4 wrapper. This may allow attacker to reach IPv6 destination that otherwise would be blocked. Moderate n/a May see proof-of-concept released publicly.
More to come...

Topics: Enterprise Software, Microsoft, Security, Windows


Ryan Naraine is a journalist and social media enthusiast specializing in Internet and computer security issues. He is currently security evangelist at Kaspersky Lab, an anti-malware company with operations around the globe. He is taking a leadership role in developing the company's online community initiative around secure content managem... Full Bio

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