__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft IE Can Divulge Location of Cached Content March 22, 2001 19:00 GMT Number L-061 ______________________________________________________________________________ PROBLEM: Because IE can divulge the physical location of cached content, an attacker could potentially plant and execute code of her choice. To execute code, a user on the victim system must either have visited the attacker’s web site or opened an HTML e-mail from her. The code has the same privileges as the user. PLATFORMS: Microsoft Internet Explorer 5.01 Microsoft Internet Explorer 5.5 Microsoft Windows Scripting Host 5.1 Microsoft Windows Scripting Host 5.5 DAMAGE: Damage varys, depending on the privileges of the user on the victim server. Examples include adding, deleting or changing files, communicating with web sites, or executing commands such as reformatting the hard drive. SOLUTION: Apply the patches provided below. ______________________________________________________________________________ VULNERABILITY MEDIUM to HIGH. Depends on the privileges of the User on the ASSESSMENT: victim machine. Potentially this could be very damaging, as it is remotely executable. ______________________________________________________________________________ [****** Start Microsoft Advisory Here ******] - ---------------------------------------------------------------------- Title: IE can Divulge Location of Cached Content Date: 06 March 2001 Software: IE and Windows Scripting Host Impact: Run code of attacker's choice. Three other vulnerabilities, of lesser severity and exploitable in more restricted circumstances, also are eliminated by the patches. Bulletin: MS01-015 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-015.asp. - ---------------------------------------------------------------------- Issue: ====== The IE security architecture provides a caching mechanism that is used to store content that needs to be downloaded and processed on the user's local machine. The purpose of the cache is to obfuscate the physical location of the cached content, in order to ensure that the web page or HTML e-mail will work through the IE security architecture to access the information. This ensures that the uses of the information can be properly restricted. A vulnerability exists because it is possible for a web page or HTML e-mail to learn the physical location of cached content. Armed with this information, an attacker could cause the cached content to be opened in the Local Computer Zone. This would enable him to launch compiled HTML help (.CHM) files that contain shortcuts to executables, thereby enabling him to run the executables. In addition to eliminating this vulnerability, the patches provided below eliminate three other vulnerabilities that either pose significantly less risk or could only be exploited in very restricted situations: - A variant of the "Frame Domain Verification" vulnerability discussed in Microsoft Security Bulletins MS00-033, MS00-055, and MS00-093. The vulnerability could enable a malicious web site operator to open two browser windows, one in the web site's domain and the other on the user's local file system, and to pass information from the latter to the former. This could enable the web site operator to read, but not change, any file on the user's local computer that could be opened in a browser window. - A vulnerability that is identical in effect to the "Frame Domain Verification" vulnerability, but which actually results from a flaw in Windows Scripting Host rather than IE. Because it could only be exploited via IE, we have provided the patch here. - A vulnerability that affects how Telnet sessions are invoked via IE. By design, telnet sessions can be launched via IE. However, a vulnerability exists because when doing so, IE will start Telnet using any command-line options the web site specifies. This only becomes a concern when using the version of the Telnet client that installs as part of Services for Unix (SFU) 2.0 on Windows NT(r) 4.0 or Windows(r) 2000 machines. The version of the Telnet client in SFU 2.0 provides an option for creating a verbatim transcript of a Telnet session. An attacker could start a session using the logging option, then stream an executable file onto the user's system in a location that would cause it to be executed automatically the next time the user booted the machine. The flaw does not lie in the Telnet client, but in IE, which should not allow Telnet to be started remotely with command-line arguments. Mitigating Factors: ==================== - None of the vulnerabilities could be exploited without some user action - either browsing to the attacker's site or opening a mail from him. Customers who exercise safe browsing habits would be less likely visit untrustworthy sites, and customers who have used the Security Zones feature to restrict what HTML mail can do would be less likely to be affected by this vulnerability. - The variants of the "frame domain verification" vulnerability discussed above could only be used to view files, and only file types that can be opened in a browser window. - The vulnerability affecting Telnet invocation is only a concern for customers who are using the Telnet client that ships as part of Services for Unix 2.0. Other versions of Telnet do not include the command-line feature to create log files. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-015.asp for information on obtaining this patch. - --------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. [****** End Microsoft Advisory Here ******] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, 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. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ (or http://ciac.llnl.gov -- they're the same machine) Anonymous FTP: ftp.ciac.org (or ciac.llnl.gov -- they're the same machine) PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. 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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