Microsoft Windows Server 2008 R2 and Windows 7 contain a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability exists in the SMB client. An unauthenticated, remote attacker could exploit this vulnerability by creating a malicious SMB server and convincing a targeted user to connect to that server. An exploit could cause the targeted user's operating system to stop responding to requests, resulting in a DoS condition.
Exploit code is publicly available.
Microsoft has confirmed this vulnerability in a security bulletin and released updated software.
Indicators of Compromise
The following versions of Windows are affected:
Windows 2000 SP4 and prior
Windows XP SP3 and prior
Windows XP Professional x64 Edition SP2 and prior
Windows Server 2003 SP2 and prior
Windows Server 2003 x64 Edition SP2 and prior
Windows Vista SP2 and prior
Windows Vista x64 Edition SP2 and prior
Windows Server 2008 for 32-bit Systems SP2 and prior
Windows Server 2008 for x64-based Systems SP2 and prior
Windows 7 for 32-bit Systems
Windows 7 for x64-based Systems
Windows Server 2008 R2 for x64-based Systems
Windows Server 2008 R2 for Itanium-based Systems
The vulnerability exists in the KeAccumulateTicks() function of the SMB client. The client fails to properly handle incomplete responses sent by a SMB server. An unauthenticated, remote attacker could create a malicious SMB or SMB2 server and convince the targeted user to connect to either server. If successful, the targeted user's system could stop responding to requests, leading to a DoS condition.
To exploit this vulnerability, the attacker must convince a targeted user to connect to a malicious SMB server. An attacker could embed a connection request in a web page and convince the targeted user to visit that page. Attempts to exploit this vulnerability will likely require the use of social engineering tactics, such as sending a link to the site via e-mail, instant messaging, or other forms of communication.
Administrators are advised to apply the appropriate updates.
Users are advised not to connect to untrusted SMB servers.
Users are advised not to open e-mail messages from suspicious or unrecognized sources. If users cannot verify that links or attachments included in e-mail messages are safe, they are advised not to open them.
Users should verify that unsolicited links are safe to follow.
Microsoft has released a security bulletin at the following link: MS10-020
Microsoft has released a security advisory at the following link: 977544
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.