I can’t help myself. And I fully understand that some of you, dear readers, might get a bit annoyed by always hearing the same tune from our side. This post is, surprise!, about yesterday’s Microsoft Patch Tuesday which – as can be seen here and here – disclosed quite a number of vulnerabilities in various Microsoft components. To make the point evoked in this post’s title I’d like to draw your attention to two particular bulletins, both rated as critical.
The advisory states that “this security update resolves a publicly disclosed vulnerability in Microsoft .NET Framework. The vulnerability could allow remote code execution on a client system if a user views a specially crafted Web page using a Web browser that can run XAML Browser Applications (XBAPs)”.
Looking at the “Workarounds” section, it turns out that the configuration of some specific parameters within Internet Explorer (those are: Loose XAML, XAML browser applications, XPS documents, Run components not signed with Authenticode, Run components signed with Authenticode) would prevent a successful attack, including potentially future ones against the vulnerable components. Disabling those parameters (amongst others) is exactly what this document suggests.
To quote from the advisory itself: “this security update resolves a privately reported vulnerability in Microsoft Windows GDI+. The vulnerability could allow remote code execution if a user viewed a specially crafted image file using affected software or browsed a Web site that contains specially crafted content”.
Here, in the “Workarounds” section disabling metafile processing is listed as a potential one. Which, in turn, we’ve recommended here.
So, to cut the chase: once more proper hardening could have been your friend, at least for those two “critical” ones.And yes, we’ve already taken the potential business impact of these measures into account. We can safely state that in many environments there’s practically none. But not having to worry about some of yesterday’s advisories and maybe even avoiding getting owned (for MS11-029 Microsoft estimates that it’s “likely to see [a] reliable exploit developed in [the] next 30 days”) might have some benefit in pretty much every organization. Think about it!