[NT] Vulnerability in Server Message Block Could Allow Elevation of Privilege (MS06-030)

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Vulnerability in Server Message Block Could Allow Elevation of Privilege
(MS06-030)
------------------------------------------------------------------------


SUMMARY

Improper handling of SMB drives allows attackers to elevate privileges and
to cause a DoS in Microsoft SMB.

DETAILS

Vulnerable Systems:
* Microsoft Windows 2000 Service Pack 4
<http://www.microsoft.com/downloads/details.aspx?FamilyId=6ec86784-6b12-410b-8068-028c58ed5df7> Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2
<http://www.microsoft.com/downloads/details.aspx?FamilyId=c17ddc07-204b-4a7f-8c5a-36b7865a030c> Download the update
* Microsoft Windows XP Professional x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=89fbbdd0-7504-4807-9337-08324aa457e7> Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1
<http://www.microsoft.com/downloads/details.aspx?FamilyId=%2043d69a41-6acb-4c64-89dc-2b9aef6e98fd> 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=e1d13c18-72d1-40b8-95b3-08aef8db9213> Download the update
* Microsoft Windows Server 2003 x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=b6018a61-b0ec-467e-9025-059d3c9f1c5f> Download the update

Immune Systems:
* Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and
Microsoft Windows Millennium Edition (Me)

SMB Driver Elevation of Privilege Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2373>
CVE-2006-2373
There is an elevation of privilege vulnerability in Server Message Block
(SMB) that could allow an attacker who successfully exploited this
vulnerability to take complete control of the affected system.

Mitigating Factors for SMB Driver Elevation of Privilege Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2373>
CVE-2006-2373:
For an attack to be successful an attacker must have valid logon
credentials and be able to log on locally to exploit this vulnerability.

Workarounds for SMB Driver Elevation of Privilege Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2373>
CVE-2006-2373:
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.

Note The following steps require Administrator privileges. In order to
block the known attack vectors both of the recommended workarounds must be
performed. We recommend that you restart the computer after you apply the
workaround.

* Disable the Workstation service

Disabling the Workstation service will help protect the affected system
from attempts to exploit this vulnerability. To disable the Workstation
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 Workstation.
5. In the Startup type list, click Disabled.
6. Click Stop, and then click OK.

You can also stop and disable the Workstation service by using the
following command at the command prompt:

sc stop lanmanworkstation & sc config lanmanworkstation start= disabled

Impact of Workaround: If you disable the Workstation service, clients will
not be able to access SMB shares.

Delete the MRxSmb driver registry entry

Deleting the MRxSmb registry entry will help protect the affected system
from attempts to exploit this vulnerability. To delete the MRxSmb key,
follow these steps:

Note Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall your operating system. Microsoft cannot guarantee
that problems resulting from the incorrect use of Registry Editor can be
solved. Use Registry Editor at your own risk. For information about how to
edit the registry, view the "Changing Keys And Values" Help topic in
Registry Editor (Regedit.exe) or view the "Add and Delete Information in
the Registry" and "Edit Registry Data" Help topics in Regedt32.exe

1. Click Start, click Run, type regedit" (without the quotation marks),
and then click OK.
2. Navigate to HKLM\System\CurrentControlSet\Services.
3. Right click on the MRxSmb key and Export the key.
4. Right click on the MRxSmb key and Delete the key.

Impact of Workaround: If you delete the MRxSmb registry key, clients will
not be able to access SMB shares.

FAQ for SMB Driver Elevation of Privilege Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2373>
CVE-2006-2373:
What is the scope of the vulnerability?
This is an elevation of privilege vulnerability. An attacker who
successfully exploited this vulnerability could 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 SMB requests.

What is SMB?
Server Message Block (SMB), and its follow-on, 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.

Who could exploit the vulnerability?
To try to exploit the vulnerability, an attacker must be able to log on
locally to a system and run a program.

How could an attacker exploit the vulnerability?
To exploit this vulnerability, an attacker would first have to log on to
the system. An attacker could then run a specially crafted application
that could exploit the vulnerability and gain complete control over the
affected system.

What systems are primarily at risk from the vulnerability?
Microsoft Windows 2000, Windows XP and Windows Server 2003 that allow
users to logon interactively including systems that function as Terminal
Servers 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?
No. An attacker must be able to log on to the specific system that is
targeted for attack. An attacker cannot load and run a program remotely by
using this vulnerability.

What does the update do?
The update addresses the vulnerability by modifying the way that the
affected operating systems handle SMB related requests.

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.

SMB Invalid Handle Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2374>
CVE-2006-2374:
There is denial of service vulnerability in Server Message Block (SMB)
that could allow an attacker who successfully exploited this vulnerability
to cause an affected system to stop responding.

Mitigating Factors for SMB Invalid Handle Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2374>
CVE-2006-2374:
For an attack to be successful an attacker must have valid logon
credentials and be able to log on locally to exploit this vulnerability.

Workarounds for SMB Invalid Handle Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2374>
CVE-2006-2374:
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.

Note The following steps require Administrator privileges. In order to
block the known attack vectors both of the recommended workarounds must be
performed. We recommend that you restart the computer after you apply this
workaround.

* Disable the Workstation service

Disabling the Workstation service will help protect the affected system
from attempts to exploit this vulnerability. To disable the Workstation
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 Workstation.
5. In the Startup type list, click Disabled.
6. Click Stop, and then click OK.

You can also stop and disable the Workstation service by using the
following command at the command prompt:

sc stop lanmanworkstation & sc config lanmanworkstation start= disabled

Impact of Workaround: If you disable the Workstation service, clients will
not be able to access SMB shares.

Delete the MRxSmb driver registry entry

Deleting the MRxSmb registry entry will help protect the affected system
from attempts to exploit this vulnerability. To delete the MRxSmb key,
follow these steps:

Note Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall your operating system. Microsoft cannot guarantee
that problems resulting from the incorrect use of Registry Editor can be
solved. Use Registry Editor at your own risk. For information about how to
edit the registry, view the "Changing Keys And Values" Help topic in
Registry Editor (Regedit.exe) or view the "Add and Delete Information in
the Registry" and "Edit Registry Data" Help topics in Regedt32.exe

1. Click Start, click Run, type regedit" (without the quotation marks),
and then click OK.
2. Navigate to HKLM\System\CurrentControlSet\Services.
3. Right click on the MRxSmb key and Export the key.
4. Right click on the MRxSmb key and Delete the key.

Impact of Workaround: If you delete the MRxSmb registry key, clients will
not be able to access SMB shares.

FAQ for SMB Invalid Handle Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2374>
CVE-2006-2374:
What is the scope of the vulnerability?
This is a <http://go.microsoft.com/fwlink/?LinkId=21142> denial of
service vulnerability. An attacker who exploited this vulnerability could
cause the affected system to stop responding. During that time, the
affected system cannot respond to requests. Note that the denial of
service vulnerability would not allow an attacker to execute code or to
elevate their user rights, but it could cause the affected system to stop
responding.

What causes the vulnerability?
The vulnerability results because of the process that the affected
operating systems use to validate certain SMB requests.

What is SMB?
Server Message Block (SMB), and its follow-on, 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.

Who could exploit the vulnerability?
To try to exploit the vulnerability, an attacker must be able to log on
locally to a system and run a program.

How could an attacker exploit the vulnerability?
To exploit this vulnerability, an attacker would first have to log on to
the system. An attacker could then run a specially crafted application
that could exploit the vulnerability and gain complete control over the
affected system.

What systems are primarily at risk from the vulnerability?
Microsoft Windows 2000, Windows XP and Windows Server 2003 that allow
users to logon interactively including systems that function as Terminal
Servers 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?
No. An attacker must be able to log on to the specific system that is
targeted for attack. An attacker cannot load and run a program remotely by
using this vulnerability.

What does the update do?
The update addresses the vulnerability by modifying the way that the
affected operating systems handle SMB related requests.

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 Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/Bulletin/MS06-030.mspx>
http://www.microsoft.com/technet/security/Bulletin/MS06-030.mspx



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