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Credit:
The information has been provided by Microsoft Security.
The original article can be found at: http://www.microsoft.com/technet/security/Bulletin/MS06-036.mspx
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Vulnerable Systems:
* Microsoft Windows 2000 Service Pack 4 Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service Pack 2 Download the update
* Microsoft Windows XP Professional x64 Edition Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service Pack 1 Download the update
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft Windows Server 2003 with SP1 for Itanium-based Systems Download the update
* Microsoft Windows Server 2003 x64 Edition Download the update
Immune Systems:
* Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft Windows Millennium Edition (Me)
Buffer Overrun in DHCP Client Service Vulnerability - CVE-2006-2372:
There is a remote code execution vulnerability in the DHCP Client service that could allow an attacker who successfully exploited this vulnerability to take complete control of the affected system.
Mitigating Factors for Buffer Overrun in DHCP Client service Vulnerability - CVE-2006-2372:
For an attack to be successful the attacker must send the affected host a specially crafted DHCP response communication from the same network subnet.
Workarounds for Buffer Overrun in DHCP Client Service Vulnerability- CVE-2006-2372:
Microsoft has tested the following workarounds. Although these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.
* Use a static IP address
To configure the system to use a static IP address follow these steps:
1. Obtain a static IP address from your network administrator
2. Click Start, and then click Control Panel and then click Network and Internet Connections.
3. Right-click the connection on which you want to specify to use a static IP address, and then click Properties.
4. Select Internet Protocol (TCP/IP) and click Properties.
5. On the General tab, click on the Use the following IP address and Use the following DNS server addresses radio buttons.
6. Input your static IP address, subnet mask, default gateway, and DNS servers.
7. Click Ok twice.
8. Repeat steps 3 through 7 for each of your network adapters.
* Disable the DHCP Client service
Disabling the DHCP Client service will help protect the affected system from attempts to exploit this vulnerability. To disable the DHCP Client service, follow these steps:
1. Click Start, and then click Control Panel. Alternatively, point to Settings, and then click Control Panel.
2. Double-click Administrative Tools.
3. Double-click Services.
4. Double-click DHCP Client.
5. In the Startup type list, click Disabled.
6. Click Stop, and then click OK.
You can also stop and disable the DHCP service by using the following command at the command prompt:
sc stop DHCP & sc config DHCP start= disabled
Impact of Workaround: If you disable the DHCP service, you cannot automatically retrieve an IP address from a DHCP Server. Without an IP address you will not be able to connect to the network.
FAQ for Buffer Overrun in DHCP Client Service Vulnerability - CVE-2006-2372:
What is the scope of the vulnerability?
This is a remote code execution vulnerability in the DHCP Client Service. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
What causes the vulnerability?
An unchecked buffer in the DHCP Client service.
What is DHCP?
Dynamic Host Configuration Protocol (DHCP) is an Internet Protocol standard that is designed to reduce the complexity of administering network addresses. DHCP does this by using a server computer to centrally manage IP addresses and other related configuration details used on your network. Windows Server provides the DHCP Server service, which enables the server computer to perform as a DHCP Server and to provide configuration settings to DHCP-enabled client computers using the DHCP Client service on your network as described in the DHCP IETF RFC 2131.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take complete control of the affected system.
Who could exploit the vulnerability?
An anonymous user could exploit the vulnerability by sending a malformed DHCP communication to an affected client on the same network segment. An attack is limited to a local subnet in a typical default network configuration scenario where DHCP or BOOTP forwarding is not enabled.
How could an attacker exploit the vulnerability?
An attacker could exploit the vulnerability by answering a client s DHCP request on the local subnet with a specially crafted DHCP response.
What systems are primarily at risk from the vulnerability?
Microsoft Windows 2000, Windows XP and Windows Server 2003 are primarily at risk from this vulnerability.
Are Windows 98, Windows 98 Second Edition or Windows Millennium Edition critically affected by this vulnerability?
No. Windows 98, Windows 98 Second Edition, and Windows Millennium Edition do not contain the affected component.
Could the vulnerability be exploited over the Internet?
An attacker could try to exploit this vulnerability over the Internet. Firewall best practices and standard default firewall configurations can help protect against attacks that originate from the Internet. Microsoft has provided information about how you can help protect your PC. End users can visit the Protect Your PC Web site. IT professionals can visit the Security Guidance Center Web site.
What does the update do?
The update removes the vulnerability by validating the way that the DHCP client handles DHCP related communications.
When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure. Microsoft had not received any information to indicate that this vulnerability had been publicly disclosed when this security bulletin was originally issued. This security bulletin addresses the privately disclosed vulnerability as well as additional issues discovered through internal investigations
When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
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