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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.184 -- CERT Advisory CA-2000-14 Microsoft Outlook and Outlook Express Cache Bypass Vulnerability 27 July 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Outlook Express 4.0 to 5.01 Outlook 97 Outlook 98 Outlook 2000 Vendor: Microsoft Operating System: MS Windows Platform: N/A Impact: Read and Create Arbitrary files Access Required: Remote Ref: ESB-2000.181 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 CERT Advisory CA-2000-14 Microsoft Outlook and Outlook Express Cache Bypass Vulnerability Original release date: July 26, 2000 Source: CERT/CC A complete revision history is at the end of this file. Systems Affected * Any system running Microsoft Outlook Express 4.0 or 4.01 * Any system running Microsoft Outlook Express 5.0 or 5.01 * Any system running Microsoft Outlook 98 * Any system running Microsoft Outlook 2000 Overview Microsoft has recently released Microsoft Security Bulletin MS00-046, in which they announced a patch for the "Cache Bypass" vulnerability. By exploiting this vulnerability, an attacker can use an HTML-formatted message to read certain types of files on the victim's machine. In addition, because this vulnerability also allows the attacker to store files on the victim's machine, it can be used in conjunction with existing vulnerabilities to execute arbitrary code on the target system. I. Description "Cache Bypass" Vulnerability Typically, all files downloaded by either Outlook or Internet Explorer are stored in an area known as a cache. The cache serves two main purposes. First, it provides temporary storage for online content, which minimizes the amount of data that must be transferred when refreshing a page. Second, it provides an area where Internet content can be downloaded to the local machine and accessed with the same security policy as remote content. This vulnerability allows attackers to use an HTML-formatted message to store files outside the cache. Inside the cache, the files are governed by the security policy of the "Internet Zone," but outside they are governed by the "Local Computer Zone." Once a file is stored in the "Local Computer Zone," the security policy of the "Internet Zone" no longer applies to it. This could put systems at risk because the security policies of the "Local Computer Zone" are typically more permissive than those of the "Internet Zone." II. Impact When exploited, this vulnerability allows an attacker to store an HTML file in an area that is not protected by the policies of the "Internet Zone." This file may then be used to open arbitrary files on the victim's machine and send their contents back to the attacker. In addition, the "Cache Bypass" vulnerability could be used in conjunction with other vulnerabilities to allow an intruder to execute arbitrary code on the victim's machine. III. Solution Microsoft has released Microsoft Security Bulletin MS00-046, which points to a patch for this vulnerability. We strongly encourage you to read this bulletin and apply the patch. MS00-046 is available at http://www.microsoft.com/technet/security/bulletin/MS00-046.asp _________________________________________________________________ The CERT Coordination Center would like to thank Microsoft for its assistance in developing this advisory. _________________________________________________________________ Author: Jeffrey P. Lanza ______________________________________________________________________ This document is available from: http://www.cert.org/advisories/CA-2000-14.html ______________________________________________________________________ CERT/CC Contact Information Email: email@example.com Phone: +1 412-268-7090 (24-hour hotline) Fax: +1 412-268-6989 Postal address: CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 U.S.A. CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends. Using encryption We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from http://www.cert.org/CERT_PGP.key If you prefer to use DES, please call the CERT hotline for more information. Getting security information CERT publications and other security information are available from our web site http://www.cert.org/ To be added to our mailing list for advisories and bulletins, send email to firstname.lastname@example.org and include SUBSCRIBE your-email-address in the subject of your message. * "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office. ______________________________________________________________________ NO WARRANTY Any material furnished by Carnegie Mellon University and the Software Engineering Institute is furnished on an "as is" basis. Carnegie Mellon University makes no warranties of any kind, either expressed or implied as to any matter including, but not limited to, warranty of fitness for a particular purpose or merchantability, exclusivity or results obtained from use of the material. Carnegie Mellon University does not make any warranty of any kind with respect to freedom from patent, trademark, or copyright infringement. _________________________________________________________________ Conditions for use, disclaimers, and sponsorship information Copyright 2000 Carnegie Mellon University Revision History July 26, 2000: Initial release - -----BEGIN PGP SIGNATURE----- Version: PGP for Personal Privacy 5.0 Charset: noconv iQA/AwUBOX9F6lr9kb5qlZHQEQLXSgCgrkytIlZTYOSAvrebXjEzXu0rBIkAnA5z YdtiKj2ytj7v892ddduvIVbx =TZ5N - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- 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 use any or all of this information is the responsibility of each user or organisation, and should be done so in accordance with site policies and procedures. 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 original authors 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/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: email@example.com 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). 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