September 26, 2016

Microsoft fixes critical RDP remote code execution vulnerability

Microsoft has released updates for its Windows operating system, and its components, to fix 26 different security related vulnerabilities. Among the bugs fixed is a vulnerability in the Remote Desktop Protocol. The vulnerability, which can be exploited by an attacker sending a sequence of specially crafted RDP packets to an affected system, can allow the attacker to execute code on the target machine.

Microsoft are rating the update as Critical and affected systems include all supported editions of Windows Server 2003 and Windows Server 2008, Windows Server 2008 R2 and Windows 7 SP1. For XP and Vista the vulnerability is less serious and Microsoft have lowered the rating to Moderate. interestingly Windows 7 PCs without SP1 are also rated as Moderate implying that code from Windows server was used in SP1 where as XP, Vista and Windows 7 without SP1 had a different, less vulnerable, code base. Microsoft point out that by default, the Remote Desktop Protocol (RDP) is not enabled on any Windows operating system. Systems that do not have RDP enabled are not at risk.

Microsoft has also updated Internet Explorer. 13 vulnerabilities have been fixed that affect all supported versions of IE. The fixes include changes to the way that Internet Explorer handles objects in memory, HTML sanitization using toStaticHTML, the way that Internet Explorer renders data during certain processes, and the way that Internet Explorer creates and initializes strings. These problems have a severity rating of Critical for Internet Explorer 6, Internet Explorer 7, Internet Explorer 8, and Internet Explorer 9 on Windows XP, Vista and 7, and could result in remote code execution. An attacker who successfully exploited any of these vulnerabilities could gain the same user rights as the current user. For Windows Server platforms Microsoft have rated these issues as Moderate.

The other Critical update is for .NET to fix a vulnerability that could allow remote code execution on a client system if a user views a specially crafted webpage using a web browser that can run XAML Browser Applications (XBAPs). The vulnerability could also be used by Windows .NET applications to bypass Code Access Security (CAS) restrictions.

As well as releasing these patch Microsoft also issued a security advisory about a vulnerability in Microsoft XML Core Services 3.0, 4.0, 5.0, and 6.0 that is being exploited in the wild. Hackers can execute code on a victim’s PCs who visit a web site, using IE, that has specially crafted webpages. 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 vulnerability affects all supported releases of Microsoft Windows, and all supported editions of Microsoft Office 2003 and Microsoft Office 2007.

Microsoft does not yet have a  patch for this problem, but there is a FixIt workaround tha basically disables the vulnerable component in IE. The vulnerability was discovered by Google, which said it saw the flaw being exploited in the wild in targeted attacks.

Microsoft’s RDP Bug Exposing 5 Million Hosts to Potential Attack

(LiveHacking.Com) – The impact of the RDP bug which Microsoft patched as part of this month’s Patch Tuesday is continuing to grow. Dan Kaminsky, who is best known for his work finding a critical DNS and for helping to fix it, has initiated a scan of the Internet and by extrapolating the data from the 8% sample (some 300 million IP addresses) it seems that there are about five million RDP endpoints on the Internet today.

With a proof of concept exploit already circulating in the wild this means that, unless updated to apply the latest patches, these five million servers are vulnerable to a real, palpable attack. Not a theoretical vulnerability but real exposure. Since RDP is the way most Windows systems are remotely administered, this vulneravility is now being seen on a whole different scale.

“There’s a very good chance that your network is exposing some RDP surface. If you have any sort of crisis response policy, and you aren’t completely sure you’re safe from the RDP vulnerability, I advise you to invoke it as soon as possible,” wrote Dan on his blog.

For those who haven’t yet applied Microsoft’s patches there is a way to substantially reduce the risk on Windows Vista and later systems where RDP is enabled: By enabling Remote Desktop’s Network Level Authentication (NLA) users are forced to authenticate before a remote desktop session is established. On systems with NLA enabled, the vulnerable code is still present and could potentially be exploited for code execution. However, NLA would require an attacker to first authenticate to the server before attempting to exploit the vulnerability.  You can find instructions here to enable NLA.

Hackers Trying to Build Exploit for RDP Vulnerability

(LiveHacking.Com) – On Tuesday Microsoft patched all currently supported version of Windows to fix a vulnerability in the Remote Desktop Protocol. At the time of the patch there was no actual known exploit but now a $1467 reward has been offered to develop a working module for Metasploit that exploits this vulnerability.

The vulnerability, which is now patched, in the Remote Desktop Protocol (RDP) exists because of the way Windows processes RDP packets in memory. In theory remote attackers can execute arbitrary code by sending crafted RDP packets triggering access to an object that was not properly initialized or has been deleted.

According to SC Magazine a proof of concept exploit has been shown to trigger a blue screen of death on Windows XP and Windows Server 2003 machines. The first proof of concept to be published was posted briefly on a Chinese website before disappearing. The second, based off the Chinese POC, was described by Accuvant researcher Josh Drake.

In a lighthearted tweet Chaouki Bekrar of VUPEN wrote “writing a remote exploit for MS12-020 / RDP for Windows 7 is definitely a challenge for Chuck Norris or Steven Seagal.” Which underlines the complexity of writing an exploit for a known vulnerability.

“However, due to the attractiveness of this vulnerability to attackers, we anticipate that an exploit for code execution will be developed in the next 30 days.” said Microsoft on its Security Research & Defense blog.

For organisations which haven’t yet applied Microsoft’s patches there is a way to substantially reduce the risk on Windows Vista and later systems where RDP is enabled: You can enable Remote Desktop’s Network Level Authentication (NLA) to require authentication before a remote desktop session is established to the remote desktop server. On systems with NLA enabled, the vulnerable code is still present and could potentially be exploited for code execution. However, NLA would require an attacker to first authenticate to the server before attempting to exploit the vulnerability.

Microsoft Release a Critical Remote Desktop Fix for Patch Tuesday

(LiveHacking.Com) – Microsoft’s ‘Patch Tuesday’ was relatively small this month with just one Critical bulletin issued. The patch (MS12-020) addresses an issue in the Remote Desktop Protocol (RDP). The vulnerability, which was privately reported to Microsoft, could allow an attacker to achieve remote code execution on a machine running RDP. If the machine does not have Network Level Authentication (NLA) enabled, the attacker would not require authentication for RCE access. To launch the attack, the hacker needs to send a sequence of specially crafted RDP packets to an affected system. However by default the Remote Desktop Protocol (RDP) is not enabled on any Windows operating system and therefore systems that do not have RDP enabled are not at risk.

The rest of the bulletins issued by Microsoft comprise of four Important issues and a single Moderate one. In total these bulletins address seven issues in Microsoft Windows, Visual Studio, and Expression Design.

The remaining bulletins are:

  • MS12-017 – Vulnerability in DNS Server Could Allow Denial of Service. This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow denial of service if a remote unauthenticated attacker sends a specially crafted DNS query to the target DNS server.
  • MS12-018 – Vulnerability in Windows Kernel-Mode Drivers Could Allow Elevation of Privilege. This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow elevation of privilege if an attacker logs on to a system and runs a specially crafted application. An attacker must have valid logon credentials and be able to log on locally to exploit this vulnerability.
  • MS12-021 – Vulnerability in Visual Studio Could Allow Elevation of Privilege. This security update resolves one privately reported vulnerability in Visual Studio. The vulnerability could allow elevation of privilege if an attacker places a specially crafted add-in in the path used by Visual Studio and convinces a user with higher privileges to start Visual Studio. An attacker must have valid logon credentials and be able to log on locally to exploit this vulnerability. The vulnerability could not be exploited remotely or by anonymous users.
  • MS12-022 – Vulnerability in Expression Design Could Allow Remote Code Execution. This security update resolves one privately reported vulnerability in Microsoft Expression Design. The vulnerability could allow remote code execution if a user opens a legitimate file (such as an .xpr or .DESIGN file) that is located in the same network directory as a specially crafted dynamic link library (DLL) file. Then, while opening the legitimate file, Microsoft Expression Design could attempt to load the DLL file and execute any code it contained. For an attack to be successful, a user must visit an untrusted remote file system location or WebDAV share and open a legitimate file (such as an .xpr or .DESIGN file) from this location that is then loaded by a vulnerable application.
  • MS12-019 – Vulnerability in DirectWrite Could Allow Denial of Service. This security update resolves a publicly disclosed vulnerability in Windows DirectWrite. In an Instant Messager-based attack scenario, the vulnerability could allow denial of service if an attacker sends a specially crafted sequence of Unicode characters directly to an Instant Messenger client. The target application could become unresponsive when DirectWrite renders the specially crafted sequence of Unicode characters.

Worm Tries to Crack Weak Passwords on Remote Desktops Connections

(LiveHacking.Com) – Microsoft has published details of a worm called Morto which attempts to break into remote servers which use the Windows Remote Desktop. The worm attempts to compromise the systems by exploiting weak administrator passwords. Once a new system is compromised, it connects to a remote server in order to download additional information and update its components. It also terminates processes for locally running security applications in order to ensure its activity continues uninterrupted.

As with all accounts (both local and remote) it is essential for users and system administrators to set strong passwords. According to Microsoft the worm tries the following passwords:

*1234
0
111
123
369
1111
12345
111111
123123
123321
123456
168168
520520
654321
666666
888888
1234567
12345678
123456789
1234567890
%u%
%u%12
1234qwer
1q2w3e
1qaz2wsx
aaa
abc123
abcd1234
admin
admin123
letmein
pass
password
server
test
user

Microsoft are reporting that although the overall numbers of computers reporting detections are low in comparison to more established malware families, the traffic it generates is noticeable.