[NT] Vulnerability in WebDAV Mini-Redirector Allows Code Execution (MS08-007)

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Vulnerability in WebDAV Mini-Redirector Allows Code Execution (MS08-007)
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SUMMARY

This critical security update resolves one privately reported
vulnerability in the WebDAV Mini-Redirector. 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.

This is a critical security update for all supported editions of Windows
XP and Windows Vista and an important security update for all supported
editions of Windows Server 2003. For more information, see the subsection,
Affected and Non-Affected Software, in this section.

Recommendation. Microsoft recommends that customers apply the update
immediately

DETAILS

Affected Software
Operating System - Maximum Security Impact - Aggregate Severity Rating -
Bulletins Replaced by this Update
*
<http://www.microsoft.com/downloads/details.aspx?FamilyId=afeef3ec-6160-4c1d-94bd-0bfce641d0a2> Windows XP Service Pack 2 - Remote Code Execution - Critical - None
*
<http://www.microsoft.com/downloads/details.aspx?FamilyID=15b7d1c4-4ef4-47b2-9e3b-22eafbdb90d8> Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2 - Remote Code Execution - Critical - None
*
<http://www.microsoft.com/downloads/details.aspx?FamilyID=b7e725bf-7248-4119-aca5-b7d502c09cfc> Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2 - Remote Code Execution - Important - None
*
<http://www.microsoft.com/downloads/details.aspx?FamilyID=8af82f86-731c-46a0-a025-b62447e2af38> Windows Server 2003 x64 Edition and Windows 2003 Server x64 Edition Service Pack 2 - Remote Code Execution - Important - None
*
<http://www.microsoft.com/downloads/details.aspx?FamilyID=bca224db-fe0e-411d-a948-1c776ce974f3> Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium based Systems - Remote Code Execution - Important - None
*
<http://www.microsoft.com/downloads/details.aspx?FamilyID=ba7a2b42-1c89-45e5-b8a6-049fa500c03a> Windows Vista - Remote Code Execution - Critical - None
*
<http://www.microsoft.com/downloads/details.aspx?FamilyID=45962232-af78-42cb-bfa0-9ce7de199585> Windows Vista x64 Edition - Remote Code Execution - Critical - None

Non-Affected Software
* Microsoft Windows 2000 Service Pack 4
* Windows Vista Service Pack 1 (all editions)
* Windows Server 2008 (all editions)

Mini-Redirector Heap Overflow Vulnerability - CVE-2008-0080
A remote code execution vulnerability exists in the way that the WebDAV
Mini-Redirector handles responses. 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.

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0080>
CVE-2008-0080

Mitigating Factors for Mini-Redirector Heap Overflow Vulnerability -
CVE-2008-0080
Mitigation refers to a setting, common configuration, or general
best-practice, existing in a default state, that could reduce the severity
of exploitation of a vulnerability. The following mitigating factors may
be helpful in your situation:

* WebClient service is disabled by default in Windows Server 2003.

Workarounds for Mini-Redirector Heap Overflow Vulnerability -
CVE-2008-0080
Workaround refers to a setting or configuration change that does not
correct the underlying vulnerability but would help block known attack
vectors before you apply the update. Microsoft has tested the following
workarounds and states in the discussion whether a workaround reduces
functionality:

* Disable the WebClient Service
To disable the WebClient Service, follow these steps:

1. Click Start, click Run, type Services.msc and then click OK.

2. Right-click WebClient service and select Properties.

3. Change the Startup type to Disabled. If the service is running, click
Stop.

4. Click OK and exit the management application.

Impact of workaround. WebDAV shares will be inaccessible.

How to undo the workaround. To undo the workaround, follow these steps:

1. Click Start, click Run, type Services.msc and then click OK.

2. Right-click WebClient service and select Properties.

3. Change the Startup type to Automatic and click Apply.

4. Click Start and then click OK and exit the management application.

FAQ for Mini-Redirector Heap Overflow Vulnerability - CVE-2008-0080
What is the scope of the vulnerability?
This is a remote code execution 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 Mini-Redirector improperly handles malicious WebDAV response.

What is WebDAV?
Web Distributed Authoring and Versioning (WebDAV) is an extension to the
Hypertext Transfer Protocol (HTTP) that defines how basic file functions
such as copy, move, delete and create are performed by using HTTP.

What is a WebDAV Redirector?
A WebDAV Redirector is a remote file system over the WebDAV protocol that
allows Windows client machines to connect to your WebDAV publishing
directory through the command line. The WebDAV Redirector enables you to
manipulate files on the Web as though the files exist on a mapped network
drive.

What is the WebDAV mini-redirector?
The WebDAV mini-redirector is also known as the WebClient service. This
service lets DAV-enabled folders appear as UNC (Universal Naming
Convention) shares.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could run
arbitrary code. An attacker could then install programs; view, change, or
delete data; or create new accounts with full user rights.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by creating specially
crafted WebDAV responses.

What systems are primarily at risk from the vulnerability?
Systems on which WebClient service is enabled are primarily at risk.
Servers could be at more risk if administrators allow users to log on to
servers and to run programs. However, best practices strongly discourage
allowing this.

What does the update do?
The update removes the vulnerability by correctly validating WebDAV
response.

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 Product Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/ms08-007.mspx>
http://www.microsoft.com/technet/security/bulletin/ms08-007.mspx



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