Risk
High
Date Discovered
August 9, 2005
Description
Microsoft Windows Plug and Play (PnP) is prone to a buffer-overflow vulnerability.
This issue takes place when the PnP service handles malformed messages containing excessive data.
This vulnerability may allow local attackers to escalate privileges and remote attackers to gain unauthorized access, depending on the underlying operating system. A successful attack may allow arbitrary code to run, resulting in the attacker gaining SYSTEM privileges.
UPDATE (8/23/2005): While investigating this vulnerability, the DeepSight Threat Analyst Team has been able to carry out anonymous remote exploitation against certain nondefault configurations of Windows XP SP1. The attack vector appears when the "Guest" account is both enabled and removed from the "Deny access to this computer from the network" entry in the "User Rights Assignment" Security Policy. This can happen when Simple File and Print Sharing has been enabled, for example by sharing a folder or a printer with the local network. Note that Simple File and Print Sharing is available only on Windows XP machines that are not part of a Windows Active Directory Domain. However, configuring a Windows XP SP1 host to share network resources prior to joining an Active Directory Domain will leave it in the vulnerable state even after the Domain is joined.
Note also that Windows XP SP2 is not prone to this exploitation method. Furthermore, there is no change to Microsoft Security Bulletin MS05-039. Customers who have deployed this update are protected from this issue.
In light of this finding, Microsoft has issued new information regarding the patch for the Microsoft Windows Plug and Play Buffer Overflow Vulnerability (see Security Bulletin 906574: http://www.microsoft.com/technet/security/advisory/906574.mspx).
Recommendations
Permit local access for trusted individuals only. Where possible, use restricted environments and restricted shells.
Given the local nature of this issue, grant only trusted and accountable individuals access to affected computers.Block external access at the network boundary, unless external parties require service.
Use network access controls to regulate external access to computers at the network perimeter. Permit access for trusted or internal computers and networks only. Block TCP ports 139 and 445.Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy a network intrusion detection sensor between the affected service and the network perimeter. Audit the logs regularly for indications of potential attacks.Implement multiple redundant layers of security.
Memory-protection schemes such as nonexecutable stack/heap configurations and randomly mapped memory segments may complicate exploitation of memory-corruption vulnerabilities.Change default user IDs and passwords.
A workaround against the Guest account attack vector is to change the default password for the guest account. This will prevent attackers from connecting to the service and authenticating as Guest.Review and adjust according to policy any default configuration settings.
Although file sharing is not enabled by default, administrators should still check to ensure that it is disabled. This is necessary only for systems that are not already patched with the MS05-039 fix or have XP SP2 installed. Such systems are not vulnerable to the Guest account attack vector.Review and adjust according to policy any default configuration settings.
Ensure the Guest Account is on the "Deny access to this computer from the network" entry in the "User Rights Assignment" Security Policy. Although this is the default setting, enabling file sharing may remove this entry from the policy.
Microsoft has released fixes to address this vulnerability in supported platforms.
Cisco has release a security notice detailing their mitigation recommendations with regard to this vulnerability.
Credits
Discovery is credited to Neel Mehta of ISS X-Force.
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