Microsoft Security Bulletin MS07-039 - Critical Vulnerability in Windows Active Directory Could Allow Remote Code Execution (926122)

Microsoft Security Bulletin MS07-039 - Critical
Vulnerability in Windows Active Directory Could Allow Remote Code Execution (926122)
Published: July 10, 2007

Version: 1.0
General Information
Executive Summary

This critical security update resolves a privately reported vulnerability in implementations of Active Directory on Windows 2000 Server and Windows Server 2003 that could allow remote code execution or a denial of service condition. Attacks attempting to exploit this vulnerability would most likely result in a denial of service condition. However remote code execution could be possible. On Windows Server 2003 an attacker must have valid logon credentials to exploit this 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.

This is a critical security update for supported editions of Windows 2000 and an important security update for supported editions of Windows Server 2003. For more information, see the subsection, Affected and Non-Affected Software, in this section.

This security update addresses the vulnerability by validating the number of convertible attributes in the client LDAP request. For more information about the vulnerability, see the next section, Vulnerability Information.

Recommendation. Microsoft recommends that customers apply the update immediately.

Known Issues. None.
Top of sectionTop of section
Affected and Non-Affected Software

The following software have been tested to determine which editions are affected. Other versions or editions are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, visit Microsoft Support Lifecycle.

Affected Software
Operating System Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by This Update

Microsoft Windows 2000 Server Service Pack 4

Remote Code Execution

Critical

None

Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2

Remote Code Execution

Important

None

Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2

Remote Code Execution

Important

None

Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems

Remote Code Execution

Important

None

Non-Affected Software
Operating System

Windows 2000 Professional Service Pack 4

Windows XP Service Pack 2

Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2

Windows Vista

Windows Vista x64 Edition

Note: These editions of Windows are not affected because they do not include the Active Directory server component.
Top of sectionTop of section

Frequently Asked Questions (FAQ) Related to This Security Update

I am using an older release of the software discussed in this security bulletin. What should I do?
The affected software listed in this bulletin have been tested to determine which releases are affected. Other releases are past their support life cycle. To determine the support life cycle for your software release, visit Microsoft Support Lifecycle.

It should be a priority for customers who have older releases of the software to migrate to supported releases to prevent potential exposure to vulnerabilities. For more information about the Windows Product Lifecycle, visit the following Microsoft Support Lifecycle. For more information about the extended security update support period for these software releases, visit the Microsoft Product Support Services Web site.

Customers who require custom support for older software must contact their Microsoft account team representative, their Technical Account Manager, or the appropriate Microsoft partner representative for custom support options. Customers without an Alliance, Premier, or Authorized Contract can contact their local Microsoft sales office. For contact information, visit the Microsoft Worldwide Information Web site, select the country, and then click Go to see a list of telephone numbers. When you call, ask to speak with the local Premier Support sales manager. For more information, see the Windows Operating System Product Support Lifecycle FAQ.
Top of sectionTop of section
Vulnerability Information

Severity Ratings and Vulnerability Identifiers
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Active Directory Remote Code Execution Vulnerability – CVE-2007-0040 Active Directory Denial of Service Vulnerability – CVE- 2007-3028 Aggregate Severity Rating

Windows 2000 Server Service Pack 4

Critical

Remote Code Execution

Important

Denial Of Service

Critical

Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2

Important

Remote Code Execution

None

Important

Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2

Important

Remote Code Execution

None

Important

Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems

Important

Remote Code Execution

None

Important
Top of sectionTop of section

Windows Active Directory Remote Code Execution Vulnerability- CVE-2007-0040

A remote code execution vulnerability exists in the way that Active Directory validates a LDAP request. An attacker who successfully exploited this vulnerability could take complete control of an affected system.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2007-0040.

Mitigating Factors for Windows Active Directory Remote Code Execution Vulnerability- CVE-2007-0040

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:
•

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.
•

Attacks attempting to exploit this vulnerability would most likely result in a denial of service condition. However remote code execution could be possible.
•

On Windows Server 2003 an attacker must have valid logon credentials to exploit this vulnerability; the vulnerability can not be exploited by an anonymous user.
Top of sectionTop of section

Workarounds for Windows Active Directory Remote Code Execution Vulnerability- CVE-2007-0040

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:
•

Block the following at the firewall:

TCP port 389

This port is used to initiate connection with the affected component. Blocking it 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 TCP and UDP Port Assignments.
•

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 313190 and Microsoft Knowledge Base Article 813878.
Top of sectionTop of section

FAQ for Windows Active Directory Remote Code Execution Vulnerability- CVE-2007-0040

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 remotely. An attacker could then install programs or view, change, or delete data; or create new accounts with full user rights.

Note. Attacks attempting to exploit this vulnerability would most likely result in a denial of service condition. However remote code execution could be possible and the scope is therefore larger than only a denial of service.

What causes the vulnerability?
The LDAP service performs insufficient checks for the number of convertible attributes included in a LDAP request.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take complete control of the affected system.

How could an attacker exploit the vulnerability?
For Windows 2000 Server, any anonymous user with access to the target network could deliver a specially crafted network packet to the affected system in order to exploit this vulnerability. On Windows Server 2003, the attacker must have valid authentication credentials to try to exploit this vulnerability.

What systems are primarily at risk from the vulnerability?
LDAP is a requirement for Active Directory. Therefore, any Windows 2000 Server or Windows Server 2003 that is running as an Active Directory Server is affected by this vulnerability.

Could the vulnerability be exploited over the Internet?
Yes. An attacker could try to exploit this vulnerability over the Internet. However common firewall practices contain Active Directory requests to within the enterprise infrastructure. Firewall best practices can help protect against attacks that originate from the Internet.

What is LDAP?
LDAP (Lightweight Directory Access Protocol) is an industry-standard protocol that enables authorized users to query or modify the data in a meta directory. In Windows Server 2000 and Windows Server 2003, LDAP is one protocol used to access data in the Active Directory.

What does the update do?
The update removes the vulnerability by performing checks for the number of convertible attributes included in an LDAP request.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

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.
Top of sectionTop of section
Top of sectionTop of section

Windows Active Directory Denial of Service Vulnerability- CVE-2007-3028

A denial of service vulnerability exists in the way that Microsoft Active Directory validates a client-sent LDAP request. An attacker could exploit the vulnerability by sending a specially crafted LDAP request to a server running Active Directory. An attacker who successfully exploited this vulnerability could cause the server to temporarily stop responding.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2007-3028.

Mitigating Factors for Windows Active Directory Denial of Service Vulnerability- CVE-2007-3028

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:
•

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.
•

Windows Server 2003 editions are not affected by this vulnerability.
Top of sectionTop of section

Workarounds for Windows Active Directory Denial of Service Vulnerability- CVE-2007-3028

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:
•

Block the following at the firewall:
Top of sectionTop of section

TCP ports 389 and 3268

These ports are used to initiate connections with the affected component. Blocking these 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 TCP and UDP Port Assignments.
•

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 313190 and Microsoft Knowledge Base Article 813878.

FAQ for Windows Active Directory Denial of Service Vulnerability- CVE-2007-3028

What is the scope of the vulnerability?
This is a denial of service vulnerability. An attacker who exploited this vulnerability could cause the affected system to temporarily stop responding. During that time, the server would be unable to 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 accepting requests.

What causes the vulnerability?
The LDAP service performs insufficient checks for the number of convertible attributes in the client LDAP request.

How could an attacker exploit the vulnerability?
An attacker could try to exploit the vulnerability by sending a specially crafted request to an affected system. The message could then cause the affected system to stop responding.

What systems are primarily at risk from the vulnerability?
LDAP is a requirement for Active Directory. Therefore, any Windows 2000 Server that is running as an Active Directory Server is affected by this vulnerability.

Could the vulnerability be exploited over the Internet?
Yes. An attacker could try to exploit this vulnerability over the Internet. However common firewall practices contain Active Directory requests to within the enterprise infrastructure. Firewall best practices can help protect against attacks that originate from the Internet.

What is LDAP?
LDAP (Lightweight Directory Access Protocol) is an industry-standard protocol that enables authorized users to query or modify the data in a meta directory. In Windows Server 2000 and Windows Server 2003, LDAP is one protocol used to access data in the Active Directory.

What does the update do?
The update removes the vulnerability by validating the client sent LDAP request logic.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

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.

Acknowledgments

Microsoft thanks the following for working with us to help protect customers:
•

Peter Winter-Smith of NGSSoftware, for reporting the Windows Active Directory Denial of Service Vulnerability-CVE-2007-3028.
•

Neel Mehta of IBM Internet Security Systems x-Force, for reporting the Windows Active Directory Remote Code Execution Vulnerability-CVE-2007-0040.

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.
Top of sectionTop of section
Revisions
•

V1.0 (July 10, 2007): Bulletin published.