__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft Index Server ISAPI Extension Buffer Overflow [Microsoft Security Bulletin MS01-033] June 19, 2001 17:00 GMT Number L-098 ______________________________________________________________________________ PROBLEM: The idq.dll extension contains a buffer overflow in the code handling input URLs. PLATFORM: Windows NT, 2000; affects IIS web servers: Index Server 2.0 and Indexing Service. DAMAGE: The idq.dll executes in the system context, therefore this exploit could result in a system compromise, allowing the attacker to execute code of his/her choice. SOLUTION: Apply the patches described in Microsoft's bulletin immediately. ______________________________________________________________________________ VULNERABILITY VERY HIGH. This vulnerability is remotely exploitable, and can ASSESSMENT: result in total system or Administrator compromise. ______________________________________________________________________________ [****** Start Microsoft Advisory ******] - ---------------------------------------------------------------------- Title: Unchecked Buffer in Index Server ISAPI Extension Could Enable Web Server Compromise Date: 18 June 2001 Software: Index Server 2.0 and Indexing Service Impact: Run code of attacker's choice Bulletin: MS01-033 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-033.asp. - ---------------------------------------------------------------------- Issue: ====== As part of its installation process, IIS installs several ISAPI extensions -- .dlls that provide extended functionality. Among these is idq.dll, which is a component of Index Server (known in Windows 2000 as Indexing Service) and provides support for administrative scripts (.ida files) and Internet Data Queries (.idq files). A security vulnerability results because idq.dll contains an unchecked buffer in a section of code that handles input URLs. An attacker who could establish a web session with a server on which idq.dll is installed could conduct a buffer overrun attack and execute code on the web server. Idq.dll runs in the System context, so exploiting the vulnerability would give the attacker complete control of the server and allow him to take any desired action on it. The buffer overrun occurs before any indexing functionality is requested. As a result, even though idq.dll is a component of Index Server/Indexing Service, the service would not need to be running in order for an attacker to exploit the vulnerability. As long as the script mapping for .idq or .ida files were present, and the attacker were able to establish a web session, he could exploit the vulnerability. Clearly, this is a serious vulnerability, and Microsoft urges all customers to take action immediately. Customers who cannot install the patch can protect their systems by removing the script mappings for .idq and .ida files via the Internet Services Manager in IIS. However, as discussed in detail in the FAQ, it is possible for these mappings to be automatically reinstated if additional system components are added or removed. Because of this, Microsoft recommends that all customers using IIS install the patch, even if the script mappings have been removed. Mitigating Factors: ==================== - The vulnerability can only be exploited if a web session can be established with an affected server. Customers who have installed Index Server or Index Services but not IIS would not be at risk. This is the default case for Windows 2000 Professional. - The vulnerability cannot be exploited if the script mappings for Internet Data Administration (.ida) and Internet Data Query (.idq) files are not present. The procedure for removing the mappings is discussed in the IIS 4.0 (http://www.microsoft.com/technet/security/iischk.asp) and IIS 5.0 (http://www.microsoft.com/technet/security/iis5chk.asp) Security checklists, can be automatically removed via either the High Security Template or the Windows 2000 Internet Server Security Tool (http://www.microsoft.com/technet/security/tools.asp). Customers should be aware, however, that subsequently adding or removing system components can cause the mapping to be reinstated, as discussed in the FAQ. - An attacker's ability to extend control from a compromised web server to other machines would depend heavily on the specific configuration of the network. Best practices recommend that the network architecture account for the inherent high-risk that machines in an uncontrolled environment, like the Internet, face by minimizing overall exposure though measures like DMZ's, operating with minimal services and isolating contact with internal networks. Steps like this can limit overall exposure and impede an attacker's ability to broaden the scope of a possible compromise. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-033.asp for information on obtaining this patch. Acknowledgment: =============== - eEye Digital Security (http://www.eeye.com) - --------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. 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[****** End Microsoft Advisory ******] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Center, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. 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Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 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