With attackers already exploiting the MSXML zero-day vulnerability, which affects a wide range of products, Microsoft has issued a FixIt tool for the bug that it is encouraging users to install as they prepare a full patch for the flaw.
The vulnerability is a critical one, and, because it’s present in so many of the company’s products, it is a prime target for attackers. Microsoft warned users about the bug on Tuesday, the same day it issued its monthly batch of patches, but it did not have a fix ready for the XML flaw. The bug can be exploited remotely, and attackers already have been exploiting it.
“Microsoft is aware of active attacks that leverage a vulnerability in Microsoft XML Core Services 3.0, 4.0, 5.0, and 6.0. The vulnerability could allow remote code execution if a user views a specially crafted webpage using Internet Explorer. An attacker would have no way to force users to visit such a website. Instead, an attacker would have to convince users to visit the website, typically by getting them to click a link in an email message or Instant Messenger message that takes them to the attacker’s website. The vulnerability affects all supported releases of Microsoft Windows, and all supported editions of Microsoft Office 2003 and Microsoft Office 2007,” Microsoft said in its advisory.
“The vulnerability exists when MSXML attempts to access an object in memory that has not been initialized, which may corrupt memory in such a way that an attacker could execute arbitrary code in the context of the logged-on user.”
The FixIt tool that Microsoft released Wednesday makes a small change to the way that the affected DLLs run. The vulnerability was discovered by researchers at Google, who alerted Microsoft to the problem. Google recently announced that it is going to start warning users when their accounts are targeted by state-sponsored attackers. Observers wondered how the company was identifying which attacks were from state-sponsored groups, but one indication could be the use of exploits against bugs such as the MSXML flaw. Researchers say that they have see attacks from China already targeting the vulnerability.