Microsoft has released a security bulletin with software updates to address the Microsoft Internet Information Services FTPd remote buffer overflow vulnerability.
Description
Microsoft Internet Information Services (IIS) versions 5.0, 5.1, 6.0, and 7.0 contain a vulnerability in the FTPd service that could allow an authenticated, remote attacker to cause a denial of service (DoS) condition or execute arbitrary code with elevated privileges.
The vulnerability is in the FTPd service due to a lack of bounds checking when IIS handles overly large requests to the NLST command. An authenticated, remote attacker could exploit this vulnerability to trigger a buffer overflow error that could cause a DoS condition or allow the attacker to execute arbitrary code with SYSTEM privileges.
Functional exploit code is publicly available that works on Windows 2000 SP4.
Microsoft has confirmed this vulnerability and updates are available.
Warning Indicators
Microsoft IIS versions 5.0, 5.1 and 6.0 are vulnerable when running on the following platforms:
Windows 2000 SP4 and prior
Windows XP SP3 and prior
Windows Server 2003 SP2 and prior
IntelliShield Analysis
Although this vulnerability requires the attacker to authenticate to the FTP server, if the server allows anonymous access, no authentication credentials would be required. Only systems that are configured to run an FTP server are vulnerable.
Windows 2000, Windows XP, and Windows 2003 systems do not have the FTP server component installed in default configurations. The FTP service on Windows XP and Windows 2003 systems likely runs with restricted privileges, limiting the impact of exploitation in the event of successful code execution. However, Windows 2000 systems are at greater risk as the FTP service may run with elevated privileges.
The Cisco Applied Intelligence team has created an Applied Mitigation Bulletin to address vulnerabilities that Microsoft disclosed in the October 2009 security bulletin release. This Cisco bulletin, which assists administrators in identifying or mitigating these vulnerabilities using Cisco devices, is available at the following link: Cisco Applied Mitigation Bulletin: Microsoft Security Bulletin Release for October 2009
Vendor Announcements
Microsoft has re-released a security advisory at the following link: 975191. Microsoft has released a security bulletin at the following link: MS09-053
US-CERT has released a vulnerability note at the following link: VU#276653
Impact
An authenticated, remote attacker could exploit this vulnerability to execute arbitrary code with SYSTEM privileges, allowing an attacker to gain complete control over a vulnerable system.
Technical Information
The vulnerability exists due to a lack of boundary checking in the NLST command when the FTP service processes malformed directory names. An authenticated, remote attacker with write access to the FTP storage directory could create directories with malicious names. The processing of the directory names could trigger a stack-based buffer overflow when the NLST command is issued. The attacker could leverage memory corruption resulting from the buffer overflow to execute arbitrary code.
Safeguards
Administrators are advised to apply the appropriate updates.
Administrators are advised not to enable the FTP server if it is not needed for a business purpose.
Administrators are advised not to enable anonymous FTP service if it is not needed for a business purpose.
Administrators using anonymous FTP servers are advised not to grant write privileges to users of this service.
Administrators may consider using the Microsoft Baseline Security Analyzer (MBSA) scan tool to identify common security misconfigurations and missing security updates on system endpoints.
Patches/Software
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
Signatures
Cisco Systems Cisco Intrusion Prevention System (IPS) 6.0
Version 4, September 4, 2009, 1:46 PM: Microsoft has re-released a security advisory with software updates to address the Microsoft Internet Information Services FTPd remote buffer overflow vulnerability.
Version 3, September 2, 2009, 10:21 AM: Microsoft has released a security advisory to address the Microsoft Internet Information Services FTPd remote buffer overflow vulnerability.
Version 2, September 1, 2009, 4:24 PM: Additional technical information is available regarding the Microsoft Internet Information Services FTPd remote buffer overflow vulnerability. Also US-CERT has released a vulnerability note.
Version 1, August 31, 2009 1:38 PM: Microsoft Internet Information Services version 6 contains a vulnerability in the FTPd service that could allow an authenticated, remote attacker to cause a denial of service condition or execute arbitrary code with elevated privileges Updates are not available.
Home Edition Base, SP1, SP2, SP3 | Professional Edition Base, SP1, SP2, SP3 | Professional x64 (AMD/EM64T) Base, SP2
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