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Vulnerability in the Client Service for NetWare Allows Remote Code
Execution (MS05-046)
------------------------------------------------------------------------
SUMMARY
A remote code execution vulnerability exists in the Client Service for
NetWare (CSNW) that could allow an attacker who successfully exploited
this vulnerability to take complete control of the affected system.
DETAILS
Affected Software:
* Microsoft Windows 2000 Service Pack 4 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=261A7D4D-90FC-4529-9C4A-B630196C6A83>
Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=4C1C2C16-99E7-4701-A3F8-65B803B8B881>
Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=8AB86BA3-54CD-44D7-8016-DE6E3ED51021>
Download the update
Non-Affected Software:
* Microsoft Windows XP Professional x64 Edition
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft
Windows Server 2003 with SP1 for Itanium-based Systems
* Microsoft Windows Server 2003 x64 Edition
* Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and
Microsoft Windows Millennium Edition (ME)
* Windows Services for Netware
CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1985>
CAN-2005-1985
Mitigating Factors for Client Service for NetWare Vulnerability:
* Windows XP Home Edition is not vulnerable to this issue. Windows XP
Home Edition does not contain the vulnerable component.
* By default, the Client Service for NetWare is not installed on any
affected operating system version. Only customers who manually install
this service are likely to be vulnerable to this issue.
* If CSNW is manually installed on Windows Server 2003 Service Pack 1, 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 on this operating system version.
* For customers who require the affected component, firewall best
practices and standard default firewall configurations can help protect
networks from attacks that originate outside the enterprise perimeter.
Best practices recommend that systems that are connected to the Internet
have a minimal number of ports exposed.
Workarounds for Client Service for NetWare Vulnerability:
Microsoft has tested the following workarounds. While 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.
Note CSNW is commonly associated with the Internetwork Packet Exchange
(IPX) and Sequenced Packet Exchange (SPX) protocols. However, CSNW could
be exploited by using any installed protocol. Because TCP/IP is the most
commonly used protocol, the following workarounds are based on TCP/IP. If
protocols such as IPX and SPX are being used, you should also block the
appropriate ports for those protocols. For more information about IPX and
SPX, visit the following Microsoft Web site.
* Remove the Client Service for NetWare if you do not need it.
If you no longer need the Client Service for NetWare, remove it. To do
this, follow these steps. These steps apply only to Windows XP. For other
operating system versions, follow the procedure that is included in the
product documentation.
1. Open Network Connections.
2. Right-click a local area connection, and then click Properties.
3. In the This connection uses the following items list, click Client
Service for NetWare.
4. Click the General tab, and then click Uninstall.
5. Complete the removal by following the instructions on the screen.
Impact of Workaround: Some organizations require the affected component
for important functions. Administrators should not remove the affected
component unless they fully understand the effect that doing this will
have on their environment.
* Block TCP ports 139 and 445 at the firewall:
These ports are used to initiate a connection with the affected component.
Blocking them at the enterprise firewall, both inbound and outbound, will
help prevent systems that are behind that firewall from attempts to
exploit this vulnerability. We recommend that you block all unsolicited
inbound communication from the Internet to help prevent attacks that may
use other ports. For more information about ports, visit the following Web
site.
* To help protect from network-based attempts to exploit this
vulnerability, use a personal firewall, such as the Internet Connection
Firewall, which is included with Windows XP and with Windows Server 2003.
By default, the Internet Connection Firewall feature in Windows XP and in
Windows Server 2003 helps protect your Internet connection by blocking
unsolicited incoming traffic. We recommend that you block all unsolicited
incoming communication from the Internet. In Windows XP Service Pack 2 and
Windows Server 2003, this features is called the Windows Firewall.
To enable the Internet Connection Firewall feature by using the Network
Setup Wizard, follow these steps:
1. Click Start, and then click Control Panel.
2. In the default Category View, click Network and Internet Connections,
and then click Setup or change your home or small office network. The
Internet Connection Firewall feature is enabled when you select a
configuration in the Network Setup Wizard that indicates that your system
is connected directly to the Internet.
To configure Internet Connection Firewall manually for a connection,
follow these steps:
1. Click Start, and then click Control Panel.
2. In the default Category View, click Networking and Internet
Connections, and then click Network Connections.
3. Right-click the connection on which you want to enable Internet
Connection Firewall, and then click Properties.
4. Click the Advanced tab.
5. Click to select the Protect my computer or network by limiting or
preventing access to this computer from the Internet check box, and then
click OK.
Note If you want to enable certain programs and services to communicate
through the firewall, click Settings on the Advanced tab, and then select
the programs, the protocols, and the services that are required.
* To help protect from network-based attempts to exploit this
vulnerability, enable advanced TCP/IP filtering on systems that support
this feature.
You can enable advanced TCP/IP filtering to block all unsolicited inbound
traffic. For more information about how to configure TCP/IP filtering, see
Microsoft Knowledge Base Article <http://support.microsoft.com/kb/309798>
309798.
* To help protect from network-based attempts to exploit this
vulnerability, block the affected ports by using IPSec on the affected
systems.
Use Internet Protocol security (IPSec) to help protect network
communications. Detailed information about IPSec and about how to apply
filters is available in Microsoft Knowledge Base Article
<http://support.microsoft.com/kb/313190> 313190 and Microsoft Knowledge
Base Article <http://support.microsoft.com/kb/813878> 813878.
What is the scope of the vulnerability?
A remote code execution vulnerability exists in the Client Service for
NetWare (CSNW). 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. This service is also called Gateway
Service for NetWare on Windows 2000 Server.
What causes the vulnerability?
An unchecked buffer in the Client Service for NetWare.
What is the Client Service for NetWare?
The Client Service for NetWare (CSNW) allows the client to access NetWare
file, print, and directory services. Both Microsoft and Novell provide a
client service for this purpose: Microsoft Client Service for NetWare and
Novell Client for Microsoft Windows XP, respectively. This vulnerability
affects the Microsoft Client Service for NetWare. For more information
about NetWare access, visit the following Web site. This service is also
called Gateway Service for NetWare on Windows 2000 Server.
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?
Any anonymous user who could deliver a specially crafted network messages
to the affected system could try to exploit this vulnerability. If CSNW is
manually installed on Windows Server 2003 Service Pack 1, 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 on Windows Server 2003 Service Pack 1.
How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability directly over a network
by creating a series of specially crafted network messages and sending
them to an affected system. The messages could then cause the affected
system to execute code.
What systems are primarily at risk from the vulnerability?
All systems that have the Client Service for NetWare, which is also known
as the Gateway Service for NetWare, installed are at risk from this
vulnerability. By default, this component is not installed on any affected
operating system version. Only customers who manually install this
component are likely to be vulnerable to this issue.
Could the vulnerability be exploited over the Internet?
Yes. 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 modifying the way that the
affected component validates the length of a message before it passes the
message to the allocated buffer.
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.
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 Product Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/MS05-046.mspx>
http://www.microsoft.com/technet/security/bulletin/MS05-046.mspx
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