[NT] Vulnerability in DHCP Client Service Could Allow Remote Code Execution (MS06-036)



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Vulnerability in DHCP Client Service Could Allow Remote Code Execution
(MS06-036)
------------------------------------------------------------------------


SUMMARY

Improper handling of user input allows attackers to execute arbitrary code
using DHCP Client Service.

DETAILS

Vulnerable Systems:
* Microsoft Windows 2000 Service Pack 4
<http://www.microsoft.com/downloads/details.aspx?FamilyId=7a04fae4-6914-4ffa-b0ec-61b912d47873> Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2
<http://www.microsoft.com/downloads/details.aspx?FamilyId=bf08cc28-b359-4b27-99b2-342f832cdecc> Download the update
* Microsoft Windows XP Professional x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=49b0da03-73a7-462a-9dc2-2eb5405e2505> Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1
<http://www.microsoft.com/downloads/details.aspx?FamilyId=2978c3d2-59e3-4dd4-8323-b1b2f9dfa7a5> Download the update
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft
Windows Server 2003 with SP1 for Itanium-based Systems
<http://www.microsoft.com/downloads/details.aspx?FamilyId=01e7bbbd-dfb6-4524-aa35-39323b210aa4> Download the update
* Microsoft Windows Server 2003 x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=d68730a7-bb7c-477a-a2a4-991629fc1402> 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 -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2372>
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
- <http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2372>
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-
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2372>
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 -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2372>
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
<http://www.faqs.org/rfcs/rfc2131.html> 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
<http://go.microsoft.com/fwlink/?LinkId=21169> protect your PC. End users
can visit the Protect Your PC Web site. IT professionals can visit the
<http://go.microsoft.com/fwlink/?LinkId=21171> 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.


ADDITIONAL INFORMATION

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>
http://www.microsoft.com/technet/security/Bulletin/MS06-036.mspx



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