- These vulnerabilities affect: All current versions of Windows (and related components like Silverlight)
- How an attacker exploits them: Multiple vectors of attack, including luring users into viewing malicious images
- Impact: In the worst case, an attacker can gain complete control of your Windows computer
- What to do: Install the appropriate Microsoft patches as soon as possible, or let Windows Automatic Update do it for you
Today, Microsoft released four security bulletins describing five vulnerabilities in Windows and related components, such as Silverlight. A remote attacker could exploit the worst of these flaws to potentially gain complete control of your Windows PC. We recommend you download, test, and deploy these critical updates as quickly as possible.
The summary below lists the vulnerabilities, in order from highest to lowest severity.
- MS14-013: DirectShow JPEG Handling Vulnerability
DirectShow (code-named Quartz) is a multimedia component that helps Windows handle various media streams, images, and files. It suffers from an unspecified memory corruption vulnerability having to do with how it handles specially crafted JPEG (JPG) images. By getting your users to view such a malicious image, perhaps via a web site or email, an attacker could leverage this flaw to execute code on that user’s computer, with the user’s privileges. If your users have local administrative privileges, the attacker gains full control of the users’ machines.
Microsoft rating: Critical
- MS14-015: Multiple Kernel-Mode Driver Code Execution Flaws
The kernel is the core component of any computer operating system. Windows also ships with a kernel-mode device driver (win32k.sys), which handles the OS’s device interactions at a kernel level. The Windows kernel-mode driver suffers from two security vulnerabilities. The worst is an elevation of privilege flaw having to do with it handles memory. In a nutshell, if a local attacker can run a specially crafted application, he could leverage this flaw to gain complete control of your Windows computers. However, in order to run his malicious program, the attacker first needs to gain local access to your Windows computer, or needs to trick you into running the program yourself, which somewhat lessens the severity of this vulnerability. The second issue could allow attackers to gain access to information in restricted sections of your computer’s memory, but doesn’t pose as high a risk as the first.
Microsoft rating: Important
- MS14-016: SAMR Lockout Bypass Vulnerability
The Security Account Manager or SAM file is a database file on Windows computers that contains all the hashed user credentials. The Security Account Manager Remote (SAMR) protocol is a client-to-server communication protocol Windows uses to check credentials against a SAM database. SAMR suffers from a flaw that allows attackers to bypass its user lockout feature. Windows allows you to lockout a user who has entered the wrong password a certain number of times. This makes it harder for attackers to launch “brute-force” password cracking attacks, since it limits the amount of failed password attempts. However, by sending specially crafted SAMR messages, an attacker can bypass this lockout feature, and try unlimited passwords against your Windows system. While this doesn’t directly give the attacker access to your computer, it does allow attackers on your local network to try and brute-force your passwords.
Microsoft rating: Important
- MS14-014: Silverlight DEP/ASLR Bypass Flaw
Silverlight is a cross-platform and cross-browser software framework used by developers to create rich media web applications. Address Space Layout Randomization (ASLR) is a memory obfuscation technique that some operating systems (OS) use to make it harder for attackers to find specific things in memory, which in turn makes it harder for them to exploit memory corruption flaws. Data Execution Prevention (DEP) is another such feature that makes it hard for attackers to execute code from memory. Unfortunately, Silverlight does not implement Windows’ DEP and ASLR protection properly. This means that it’s relatively easy for attackers to exploit any memory corruption flaws in Silverlight. By itself, this bypass flaw is worthless. It doesn’t give an attacker access to your computer. However, assuming attackers find memory corruption flaws in Silverlight, this bypass flaw would make it easier for them to exploit those flaws to execute code. You should apply this update simply to improve the general security of Silverlight.
Microsoft rating: Important
Microsoft has released various updates that correct all of these vulnerabilities. You should download, test, and deploy the appropriate updates throughout your network immediately. If you choose, you can also let Windows Update automatically download and install them for you. As always, you should test your updates before deploying them. Especially, server related updates.
The links below point directly to the “Affected and Non-Affected Software” section of each bulletin, where you can find links to the various updates:
For All WatchGuard Users:
Though WatchGuard’s XTM appliances offer defenses that can mitigate the risk of some of these flaws (such as allowing you to block .jpg files, or enabling GAV or IPS services to detect attacks and the malware they distribute), attackers can exploit others locally. Since your gateway XTM appliance can’t protect you against local attacks, we recommend you install Microsoft’s updates to completely protect yourself from these flaws.
Microsoft has released patches correcting these issues.
This alert was researched and written by Corey Nachreiner, CISSP (@SecAdept).
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