[NT] Vulnerability in Server Message Block Allows Remote Code Execution (MS05-027)

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Date: 15 Jun 2005 10:21:31 +0200

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  Vulnerability in Server Message Block Allows Remote Code Execution
(MS05-027)
------------------------------------------------------------------------

SUMMARY

A remote code execution vulnerability exists in Server Message Block (SMB)
that allows an attacker who successfully exploited this vulnerable to take
complete control of the affected system.

DETAILS

Affected Software:
 * Microsoft Windows 2000 Service Pack 3 and Microsoft Windows 2000
Service Pack 4
<http://www.microsoft.com/downloads/details.aspx?FamilyId=1E83F120-01FB-4029-A524-F3AE08F8BB28> Download the update

 * Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2
<http://www.microsoft.com/downloads/details.aspx?FamilyId=9CC719AD-5E57-4AEF-9FB3-9F7AB7BB5D32> Download the update

 * Microsoft Windows XP 64-Bit Edition Service Pack 1 (Itanium)
<http://www.microsoft.com/downloads/details.aspx?FamilyId=B3A61221-0DAC-452C-87E9-3362DD97273A> Download the update

 * Microsoft Windows XP 64-Bit Edition Version 2003 (Itanium)
<http://www.microsoft.com/downloads/details.aspx?FamilyId=7D97522F-F322-44D4-9E60-BDFED4A7A079> Download the update

 * Microsoft Windows XP Professional x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=716B9CDE-5EF1-4005-903F-FC720863F03C> Download the update

 * Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1
<http://www.microsoft.com/downloads/details.aspx?FamilyId=3EA61158-E7C5-49A8-A701-B16AAF83A188> 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=7D97522F-F322-44D4-9E60-BDFED4A7A079> Download the update

 * Microsoft Windows Server 2003 x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=B455A686-EFF2-44D7-BAFA-AC73F0F68FB1> Download the update

Non-Affected Software:
 * Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and
Microsoft Windows Millennium Edition (ME)

CVE Information:
Server Message Block Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1206>
CAN-2005-1206

Mitigating Factors for Server Message Block Vulnerability - CAN-2005-1206:
Because of the nature of this issue, attempts to exploit this
vulnerability would most likely result in a denial of service.
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. By default, the Windows
Firewall that is provided as part of Windows XP Service Pack 2 and Windows
Server 2003 blocks the affected ports from responding to network-based
attempts to exploit this vulnerability.

Workarounds for Server Message Block Vulnerability - CAN-2005-1206:
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 Other protocols such as Internetwork Packet Exchange (IPX) and
Sequenced Packet Exchange (SPX) could be vulnerable to this issue. If
vulnerable protocols such as IPX and SPX are in use, it is important to
block the appropriate ports for those protocols as well. For more
information about IPX and SPX, visit the following
<http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us/prch_cnn_goue.asp> Microsoft Web site.

Block TCP ports 139 and 445 at the firewall:
These ports are used to initiate a connection with the affected protocol.
Blocking them at the 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
<http://go.microsoft.com/fwlink/?LinkId=21312> Web site.
To help protect from network-based attempts to exploit this vulnerability,
use a personal firewall, such as the
<http://go.microsoft.com/fwlink/?LinkId=33335> 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.

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
 <http://support.microsoft.com/kb/309798> Microsoft Knowledge Base Article
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 <http://support.microsoft.com/kb/313190>
Microsoft Knowledge Base Article 313190 and
<http://support.microsoft.com/kb/813878> Microsoft Knowledge Base Article
813878.

FAQ for Server Message Block Vulnerability - CAN-2005-1206:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. 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?
The vulnerability results because of the process that the affected
operating systems use to validate certain incoming SMB packets.

What is SMB?
Server Message Block (SMB), and its follow-on,
<http://www.microsoft.com/mind/1196/cifs.asp> Common Internet File System
(CIFS), is the Internet Standard protocol that Windows uses to share
files, printers, serial ports, and also to communicate between computers.
To do this, SMB uses named pipes and mail slots. In a networked
environment, servers make file systems and resources available to clients.
Clients make SMB requests for resources. Servers make SMB responses. This
is described as a client server, request-response protocol.

Does this vulnerability also affect CIFS?
Common Internet File System (CIFS) is an Internet Standard protocol. The
vulnerability described here resides specifically in Microsoft's
implementation of the protocol and not the protocol itself.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take
complete control of the affected system. An attacker could also perform
remote denial of service attacks and local privilege elevation attacks by
using this vulnerability.

Who could exploit the vulnerability?
Any anonymous user who could deliver a specially crafted message to the
affected system could try to exploit this vulnerability.

How could an attacker exploit the vulnerability?
There are several different ways that an attacker could try to exploit
this vulnerability. An attacker could try to exploit the vulnerability
directly over a network by creating a series of specially crafted messages
and sending them to an affected system. The messages could then cause the
affected system to execute code.
An attacker could also access the affected component through another
vector. For example, an attacker could use another program that passes
parameters to the vulnerable component either locally or remotely.

What systems are primarily at risk from the vulnerability?
All affected operating systems are at risk from this vulnerability. By
default, the Windows Firewall that is provided as part of Windows XP
Service Pack 2 and Windows Server 20003 blocks the affected ports from
responding to network-based attempts to exploit this vulnerability.

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 Center Web site.

What does the update do?
The update addresses the vulnerability by modifying the way that the
affected operating systems validate SMB network packets before they pass
the data 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.

How does this vulnerability relate to the Server Message Block
vulnerability that is corrected by MS05-011?
Both vulnerabilities were in Server Message Block. However, this update
addresses a new vulnerability that was not addressed as part of MS05-011.
MS05-011 helps protect against the vulnerability that is discussed in that
bulletin, but does not address this new vulnerability. This update does
not replace MS05-011. You must install this update and the update that is
provided as part of the MS05-011 security bulletin to help protect your
system against both vulnerabilities.

ADDITIONAL INFORMATION

The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/ms05-027.mspx>
http://www.microsoft.com/technet/security/bulletin/ms05-027.mspx

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