Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2009.1235.3 Vulnerability in Internet Information Services FTP Service Could Allow for Remote Code Execution 7 September 2009 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Microsoft Internet Information Server 5.0 Microsoft Internet Information Server 5.1 Microsoft Internet Information Server 6.0 Microsoft Internet Information Server 7.0 Publisher: Microsoft Operating System: Windows Impact/Access: Execute Arbitrary Code/Commands -- Remote/Unauthenticated Denial of Service -- Remote/Unauthenticated Resolution: Mitigation CVE Names: CVE-2009-3023 CVE-2009-2521 Original Bulletin: http://www.microsoft.com/technet/security/advisory/975191.mspx Comment: Microsoft has updated this advisory to include a Denial of Service and further information. Revision History: September 7 2009: Updated with information regarding DoS and relevant CVE September 2 2009: Updated to the Microsoft Security Advisory September 1 2009: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- Microsoft Security Advisory (975191) Vulnerabilities in the FTP Service in Internet Information Services Published: September 01, 2009 | Updated: September 03, 2009 Version: 2.0 General Information Executive Summary Microsoft is investigating new public reports of vulnerabilities in the FTP Service in Microsoft Internet Information Services (IIS) 5.0, Microsoft Internet Information Services (IIS) 5.1, Microsoft Internet Information Services (IIS) 6.0, and Microsoft Internet Information Services (IIS) 7.0. The vulnerabilities could allow remote code execution (RCE) on systems running FTP Service on IIS 5.0, or denial of service (DoS) on systems running FTP Service on IIS 5.0, IIS 5.1, IIS 6.0 or IIS 7.0. Microsoft is aware that detailed exploit code has been published on the Internet for these vulnerabilities. Microsoft is currently aware of limited attacks that use this exploit code. Microsoft is actively monitoring this situation to keep customers informed and to provide customer guidance as necessary. We are actively working with partners in our Microsoft Active Protections Program (MAPP) to provide information that they can use to provide broader protections to customers. Upon completion of this investigation, Microsoft will take the appropriate action to help protect our customers. This may include providing a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs. These vulnerabilities were not responsibly disclosed to Microsoft and may put computer users at risk. We continue to encourage responsible disclosure of vulnerabilities. We believe the commonly accepted practice of reporting vulnerabilities directly to a vendor serves everyone's best interests. This practice helps to ensure that customers receive comprehensive, high-quality updates for security vulnerabilities without exposure to malicious attackers while the update is being developed. CVE Reference CVE-2009-3023 (RCE on IIS 5.0 and DoS on IIS 5.1 and IIS 6.0) CVE-2009-2521 (DoS on IIS 5.0, IIS 5.1, IIS 6.0, and IIS 7.0) Affected Software Operating System Component Microsoft Windows 2000 Microsoft Internet Information Service Pack 4 Services 5.0 (FTP Service 5.0) Windows XP Service Pack 2 and Microsoft Internet Information Windows XP Service Pack 3 Services 5.1 (FTP Service 5.1) Windows XP Professional x64 Edition Microsoft Internet Information Service Pack 2 Services 6.0 (FTP Service 6.0) Windows Server 2003 Microsoft Internet Information Service Pack 2 Services 6.0 (FTP Service 6.0) Windows Server 2003 x64 Edition Microsoft Internet Information Service Pack 2 Services 6.0 (FTP Service 6.0) Windows Server 2003 with SP2 Microsoft Internet Information for Itanium-based Systems Services 6.0 (FTP Service 6.0) Windows Vista, Windows Vista Microsoft Internet Information Service Pack 1, and Windows Vista Services 7.0 (FTP Service 6.0) Service Pack 2 Windows Vista x64 Edition, Microsoft Internet Information Windows Vista x64 Edition Services 7.0 (FTP Service 6.0) Service Pack 1, and Windows Vista x64 Edition Service Pack 2 Windows Server 2008 for 32-bit Systems Microsoft Internet Information and Windows Server 2008 for 32-bit Services 7.0 (FTP Service 6.0) Systems Service Pack 2 Windows Server 2008 for x64-based Microsoft Internet Information Systems and Windows Server 2008 for Services 7.0 (FTP Service 6.0) x64-based Systems Service Pack 2 Windows Server 2008 for Itanium-based Microsoft Internet Information Systems and Windows Server 2008 for Services 7.0 (FTP Service 6.0) Itanium-based Systems Service Pack 2 Mitigating Factors Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of this issue. The following mitigating factors may be helpful in your situation: * FTP Service is not installed by default on all supported editions of Microsoft Windows 2000, Windows XP, and Windows Server 2003. * Internet Information Services 5.1 on Window XP and Internet Information Services 6.0 on Windows Server 2003 are at reduced risk because these versions were compiled using the /GS compiler option. This does not remove the vulnerability but does make exploitation of the vulnerability more difficult and reduces the impact to a denial of service. Workarounds Workaround refers to a setting or configuration change that does not correct the underlying issue 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: * Do not allow FTP write access to anonymous users This workaround blocks remote code execution attacks from anonymous users. With this workaround, all affected versions of IIS are still vulnerable to denial of service attacks from anonymous users. This workaround blocks known exploits and minimizes the impact of any variations of this attack vector. However, this workaround does not render the vulnerability completely inaccessible to exploitation. Anonymous users are not granted FTP write access by default. If anonymous write access has been granted on an FTP server, the administrator can modify IIS permissions to prevent anonymous write access. Anonymous users will not be able to cause a remote code execution with this workaround. To modify IIS permissions to prevent FTP write access to anonymous users, perform the following steps: 1. Launch IIS Manager. 2. Right click Default FTP Site and point to Properties. 3. Click the Home Directory tab. 4. Ensure that Write is deselected. Impact of Workaround: Anonymous users will not have the ability to publish content on the server using the FTP Service. * Do not allow FTP access to anonymous users This workaround blocks denial of service attacks from unauthenticated users without a valid user account. This workaround blocks known exploits and minimizes the impact of any variations of this attack vector. However, this workaround does not render the vulnerability completely inaccessible to exploitation. Anonymous users are not granted FTP write access by default. If anonymous write access has been granted on an FTP server, the administrator can modify IIS permissions to prevent anonymous write access. Anonymous users will not be able to exploit the vulnerability with this workaround. To modify IIS permissions to prevent FTP write access to anonymous users, perform the following steps: 1. Launch IIS Manager. 2. Right click Default FTP Site and point to Properties. 3. Click the SecurityAccounts tab. 4. Ensure that Allow anonymous connections is deselected. Impact of Workaround: Anonymous users will not have access to the FTP Service. * Modify NTFS file system permissions to disallow directory creation by FTP users This workaround blocks remote code execution attacks from authenticated users. With this workaround, all affected versions of IIS server are still vulnerable to denial of service attacks from authenticated users. This workaround blocks known exploits and minimizes the impact of any variations of this attack vector. However, this workaround does not render the vulnerability completely inaccessible to exploitation. An administrator can modify NTFS file system permissions on the root directories of FTP sites hosted on a server to disallow creation of directories by FTP users. This modification still allows FTP users to upload files to existing directories. Authenticated and unauthenticated users will not be able to cause a remote code execution with this workaround. As administrator, perform the following steps to remove directory creation privileges from the Users group. If you have a configured FTP user or custom group to manage your FTP users, replace the Users group in Step 5 below with these custom identities. 1. Browse to the root directory of your FTP site. By default this is in %systemroot%\inetpub\ftproot. 2. Right-click the directory and select Properties. 3. Click the Security tab and click Advanced. 4. Click Change Permissions. 5. Select the Users group and click Edit. 6. Deselect Create Folders/Append Data. Impact of Workaround: FTP users will not be able to create directories through the FTP Service. FTP users will still be able to upload files to existing directories through the FTP Service. * Upgrade to FTP Service 7.5 FTP Service 7.5 is available for Windows Vista and Windows Server 2008. This version of FTP Service is not affected by the vulnerabilities in this advisory. See the following sites on Download Center: - Microsoft FTP Service 7.5 for IIS 7.0 (x86) [1] - Microsoft FTP Service 7.5 for IIS 7.0 (x64) [2] Impact of Workaround: FTP sites will need to be migrated from FTP Service 6.0 to FTP Service 7.5. * Disable the FTP Service This workaround will completely block the known attack vector or any variations thereof. See Microsoft Knowledge Base Article 321141, "How To Disable or Remove Unnecessary IIS Services." Impact of Workaround: FTP Service will be disabled. [1] Microsoft FTP Service 7.5 for IIS 7.0 (x86) http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=b7f5b652-8c5c-447a-88b8-8cfc5c13f571 [2] Microsoft FTP Service 7.5 for IIS 7.0 (x64) http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=ffb7c167-279e-48d3-8169-dea85784c4d1 - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iD8DBQFKpIreNVH5XJJInbgRAhW+AJ0enntMmOdux8vhalzRjF6H5nAlvwCfdV5u S1qh0GMnooGvRlGpjXo/sYI= =Ubvt -----END PGP SIGNATURE-----