Multiple Vendor Insecure Call to CreateProcess() Vulnerability iDEFENSE Security Advisory 11.15.05 www.idefense.com/application/poi/display?id=340&type=vulnerabilities November 15, 2005 I. BACKGROUND The Microsoft Windows API includes the CreateProcess() function as a means to create a new process and it's primary thread. CreateProcessAsUser() is similar but allows for the process to be run in the security context of a particular user. II. DESCRIPTION The format of the CreateProcess() function is as follows: BOOL CreateProcess( LPCTSTR lpApplicationName, LPTSTR lpCommandLine, LPSECURITY_ATTRIBUTES lpProcessAttributes, LPSECURITY_ATTRIBUTES lpThreadAttributes, BOOL bInheritHandles, DWORD dwCreationFlags, LPVOID lpEnvironment, LPCTSTR lpCurrentDirectory, LPSTARTUPINFO lpStartupInfo, LPPROCESS_INFORMATION lpProcessInformation ); The 'lpApplicationName' variable contains the name of the module to be executed. However, this can be a NULL value, in which case, the module name to be executed will be the first white space-delimited token in the lpCommandLine string. It is a known issue, that if lpApplicationName contains a NULL value and the full module path in the lpCommandLine variable contains white space and is not enclosed in quotation marks, it is possible that an alternate application will be executed. Consider the following scenario: CreateProcess( NULL, c:program filessub dirprogram.exe, ... ); In this case, the system will successively expand the string when interpreting the file path, until a module is encountered to execute. The string used in the above example would be interpreted as follows: c:program.exe filessub dirprogram name c:program filessub.exe dirprogram name c:program filessub dirprogram.exe Therefore, if a file named program.exe existed in the c: directory, it would be executed instead of the intended application. This is a known issue, discussed directly in the API documentation: http://msdn.microsoft.com/library/en-us/dllproc/base/createprocessasuser .asp III. ANALYSIS Despite the fact that this is a known issue, several popular applications, insecurely call the CreateProcess() and CreateProcessAsUser() functions. This creates a scenario whereby arbitrary code could be executed. In the scenario detailed above, if an attacker were able to install arbitrary code in a file at c:program.exe, when the vulnerable application was launched, the code would be executed. The arbitrary code would generally be executed under the privileges of the executing user but could also be launched with elevated privilegs if an insecure call were made CreateProcessAsUser() using elevated privileges. This attack would involve some form of social engineering or need to be combined with another attack to first get the arbitrary code installed in the correct location. IV. DETECTION The following applications have been confirmed to be vulnerable: Vendor: RealNetworks Application: RealPlayer 10.5 Files: realplay.exe realjbox.exe Vendor: Kaspersky Application: Kaspersky Anti-Virus for Windows File Servers 5.0 (English) - Installation File Files: kav5.0trial_winfsen.exe Vendor: Apple Application: iTunes 4.7.1.30 Files: iTunesHelper.exe Vendor: VMWare Application: VMWare Workstation 5.0.0 build-13124 Files: VMwareTray.exe VMwareUser.exe Vendor: Microsoft Application: Microsoft Antispyware 1.0.509 (Beta 1) Files: GIANTAntiSpywareMain.exe gcASNotice.exe gcasServ.exe gcasSWUpdater.exe GIANTAntiSpywareUpdater.exe Note: The vulnerability in Microsoft Antispyware was previously discussed on the Full-Disclosure mailing list (http://lists.grok.org.uk/pipermail/full-disclosure/2005-May/033909.html ) but remains unpatched. V. WORKAROUND Ensure that unexpected files are not stored in locations that can be used for this attack. Windows XP SP2 will alert a user of the existence of a file named c:program.exe when it first boots, however, any path containing white space where a vulnerable application is stored could be used in this attack. VI. VENDOR RESPONSE The following vendor responses have been provided. Apple: "Due to the way iTunes 5 launches its helper application, multiple system paths are searched for which program to run. This may allow a malicious user on the local system to create an environment where an alternate program will be executed by iTunes. iTunes 6 addresses this issue and can be obtained from http://www.apple.com/itunes/download/. Credit to iDEFENSE for reporting this issue to us." Kaspersky: "We are currently looking into the problem, and it seems that this is not present in the current version of KAV for File Servers." Microsoft: "Microsoft has confirmed that the Beta 2 version of its Antispyware product, targeted for release later this year, will address the issue reported by iDEFENSE." VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the following names to this issue. RealNetworks RealPlayer 10.5 CAN-2005-2936 Kaspersky Anti-Virus 5.0 CAN-2005-2937 Apple iTunes 4.7.1.30 CAN-2005-2938 VMWare Workstation 5.0.0 build-13124 CAN-2005-2939 Microsoft Antispyware 1.0.509 (Beta 1) CAN-2005-2940 Theses are candidates for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. VIII. DISCLOSURE TIMELINE 09/19/2005 Initial vendor notification 11/15/2005 Coordinated public disclosure IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp Free tools, research and upcoming events http://labs.idefense.com X. LEGAL NOTICES Copyright © 2005 iDEFENSE, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice (at) idefense (dot) com [email concealed] for permission. Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.