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Today we released 16 security bulletins. Nine have a maximum severity rating of Critical and seven have a maximum severity rating of Important. This release addresses several publicly disclosed vulnerabilities. We hope that the table below helps you prioritize the deployment of the updates appropriately for your environment.
Please let us know (switech at microsoft dot com) if you have any questions about these updates.
Jonathan Ness, MSRC Engineering
Today we have released MS11-044 to address CVE-2011-1271, a remote code execution vulnerability in the .NET framework. Here we would like to provide more technical information about this vulnerability and why we believe this issue to be unlikely to be exploited.
This root cause of CVE-2011-1271 is that there was a bug in the JIT compiler which would cause it to mistakenly determine that a given object is always null (or non-null) and would omit certain checks.
if ((value == null || value == new string) == false)
00000027 test esi,esi ; value == null?
00000029 je 00000075
0000002b xor edx,edx ; new string
0000002d mov ecx,6D913BD2h
00000032 call FFD20BC8
00000037 cmp eax,esi ; value == new string?
00000039 je 00000075
Console.WriteLine("Post-check Value is: " + value);
0000003b mov ecx,dword ptr ds:[03532090h] ; "Post-check value is: "
00000041 xor edx,edx ; Wrong here.
00000043 call 6D70B7E8 ; String.Concat()
00000048 mov esi,eax ;
0000004a call 6D72BE08 ; get Console.Out
0000004f mov ecx,eax
00000051 mov edx,esi
00000053 mov eax,dword ptr [ecx]
00000055 call dword ptr [eax+000000D8h] ; Console.WriteLine()
At offset 0x41, the optimizer has incorrectly concluded that value will always be null so it directly passes a null to String.Concat().
For CVE-2011-1271, the JIT compiler can introduce a logic flaw when running C# or IL code sequences very similar to those describe above. Depending on the .NET application’s business logic, if the NULL check (or non-NULL check) is used to make a security decision, for example the check of certain credentials, and if the attacker controlled data may leverage directly or indirectly this missing logic and gain advantages based on this, then there is a possibility of remote code execution. However, we do not believe this to be a common case for the majority of deployed .NET applications.
Special thanks to Reid Borsuk in .NET team.
Fermin Serna and Chengyun Chu, MSRC Engineering
Today, we released MS11-050, a cumulative security update for Internet Explorer to address several vulnerabilities in IE9.
The following table lists the CVEs included in MS11-050, and whether each affects IE8 or IE9.
As shown above, only a minor fraction of vulnerabilities affecting IE8 (and earlier versions of the browser) would still affect IE9. This is due to various factors related to security work that happened in IE8, ranging from deprecating obsolete features, to improving fuzzing tests in IE9 and so on. For example, CVE-2011-1255 is related to HTML+TIME, which was deprecated in IE9 development.
There are many beautiful things in IE9. Besides all these wonderful new features, we would also recommend you to update to IE9 if you can for security. :)
Chengyun Chu, MSRC Engineering
The Khronos Group’s WebGL technology is a cross-platform, low-level 3D graphics API for the web. Recently, Context Information Security published two reports critical of the WebGL technology, WebGL – A New Dimension for Browser Exploitation and WebGL – More WebGL Security Flaws.
One of the functions of MSRC Engineering is to analyze various technologies in order to understand how they can potentially affect Microsoft products and customers. As part of this charter, we recently took a look at WebGL. Our analysis has led us to conclude that Microsoft products supporting WebGL would have difficulty passing Microsoft’s Security Development Lifecycle requirements. Some key concerns include:
The security of WebGL as a whole depends on lower levels of the system, including OEM drivers, upholding security guarantees they never really need to worry about before. Attacks that may have previously resulted only in local elevation of privilege may now result in remote compromise. While it may be possible to mitigate these risks to some extent, the large attack surface exposed by WebGL remains a concern. We expect to see bugs that exist only on certain platforms or with certain video cards, potentially facilitating targeted attacks.
As WebGL vulnerabilities are uncovered, they will not always manifest in the WebGL API itself. The problems may exist in the various OEM and system components delivered by IHV’s. While it has been suggested that WebGL implementations may block the use of affected hardware configurations, this strategy does not seem to have been successfully put into use to address existing vulnerabilities.
It is our belief that as configurations are blocked, increasing levels of customer disruption may occur. Without an efficient security servicing model for video card drivers (eg: Windows Update), users may either choose to override the protection in order to use WebGL on their hardware, or remain insecure if a vulnerable configuration is not properly disabled. Users are not accustomed to ensuring they are up-to-date on the latest graphics card drivers, as would be required for them to have a secure web experience. In some cases where OEM graphics products are included with PCs, retail drivers are blocked from installing. OEMs often only update their drivers once per year, a reality that is just not compatible with the needs of a security update process.
Modern operating systems and graphics infrastructure were never designed to fully defend against attacker-supplied shaders and geometry. Although mitigations such as ARB_robustness and the forthcoming ARB_robustness_2 may help, they have not proven themselves capable of comprehensively addressing the DoS threat. While traditionally client-side DoS is not a high severity threat, if this problem is not addressed holistically it will be possible for any web site to freeze or reboot systems at will. This is an issue for some important usage scenarios such as in critical infrastructure.
We believe that WebGL will likely become an ongoing source of hard-to-fix vulnerabilities. In its current form, WebGL is not a technology Microsoft can endorse from a security perspective.
We recognize the need to provide solutions in this space however it is our goal that all such solutions are secure by design, secure by default, and secure in deployment.
- MSRC Engineering