-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Count.cgi Buffer Overrun Vulnerabiliity October 31, 1997 22:00 GMT Number I-013 ______________________________________________________________________________ PROBLEM: A vulnerability exists in the Count.cgi cgi-bin program. PLATFORM: Any web server running the count.cgi script. DAMAGE: Remote users may be able to execute arbitrary commands with the privileges of the httpd process which answers HTTP requests. This may be used to compromise the http server and under certain configurations gain privileged access. SOLUTION: Install current version of Count.cgi, version 2.4, or apply workaround. ______________________________________________________________________________ VULNERABILITY It is recommended that sites that have the Count.cgi cgi-bin ASSESSMENT: program installed take the steps outlined in Section 3 as soon as possible. ______________________________________________________________________________ [ Start AUSCERT Advisory ] =========================================================================== AA-97.27 AUSCERT Advisory Buffer Overrun Vulnerability in Count.cgi cgi-bin Program 31 October 1997 Last Revised: -- - ---------------------------------------------------------------------------- The Australian Computer Emergency Response Team (AUSCERT) has received information that a buffer overrun vulnerability exists in the Count.cgi cgi-bin program. A new version of Count.cgi has been released addressing this vulnerability. AUSCERT recommends that sites that have the Count.cgi cgi-bin program installed take the steps outlined in Section 3 as soon as possible. - ---------------------------------------------------------------------------- 1. Description AUSCERT has received information that a vulnerability exists in the Count.cgi cgi-bin program. The Count.cgi cgi-bin program is used to record and display the number of times a WWW page has been accessed. Due to insufficient bounds checking on arguments which are supplied by users, it is possible to overwrite the internal stack space of the Count.cgi program while it is executing. By supplying a carefully designed argument to the Count.cgi program, intruders may be able to force Count.cgi to execute arbitrary commands with the privileges of the httpd process. The Count.cgi program is extremely widely used. Sites are encouraged to check for its existence and its possible exploitation. To check whether exploitation of this vulnerability has been attempted at your site, search for accesses to the Count.cgi program in your access logs. An example of how to do this is: # grep -i 'Count.cgi' {WWW_HOME}/logs/access_log Where, {WWW_HOME} is the base directory for your web server. If this command returns anything, further investigation is necessary. Specifically, look for accesses to Count.cgi that contain long strings of nonsensical characters. If sites find any evidence showing that they have been probed using this vulnerability, they are encouraged to report the incident to AUSCERT or their local incident response team. Reports of all attacks help AUSCERT gain a better overview of intruder activity within the constituency. 2. Impact Remote user may be able to execute arbitrary commands with the privileges of the httpd process which answers HTTP requests. This may be used to compromise the http server and under certain configurations gain privileged access. 3. Workarounds/Solution AUSCERT recommends that sites upgrade to the current version of Count.cgi (Section 3.1). For sites that can not immediately install the current version of Count.cgi, it is recommended that the workaround described in Section 3.2 be applied. 3.1 Upgrade to the current Count.cgi version The author of Count.cgi has recently released version 2.4 which addresses the vulnerability described in this advisory. AUSCERT recommends that sites upgrade to the latest version as soon as possible. The current version is available from: http://www.fccc.edu/users/muquit/Count.html 3.2 Remove execute permissions To prevent the exploitation of the vulnerability described in this advisory, AUSCERT recommends that the execute permissions be removed from Count.cgi immediately. Note that this will have the side effect of preventing the page hit counter from being incremented and displayed on web pages using Count.cgi. The remainder of such web pages should still display. 4. Additional measures It is important to note that attacks similar to this may succeed against any CGI program which has not been written with due consideration for security. Sites using HTTP servers, and in particular CGI applications, are encouraged to develop an understanding of the security issues involved. Sites should consider taking this opportunity to examine their httpd configuration and web servers. In particular, all CGI programs that are not required should be removed, and all those remaining should be examined for possible security vulnerabilities. It is also important to ensure that all child processes of httpd are running as a non-privileged user. This is often a configurable option. See the documentation for your httpd distribution for more details. Numerous resources relating to WWW security are available. The following pages may provide a useful starting point. They include links describing general WWW security, secure httpd setup and secure CGI programming. The World Wide Web Security FAQ: http://www-genome.wi.mit.edu/WWW/faqs/www-security-faq.html NSCA's "Security Concerns on the Web" Page: http://hoohoo.ncsa.uiuc.edu/security/ The following books contain useful information including sections on secure programming techniques. "Web Security Sourcebook", Aviel Rubin, Daniel Geer and Marcus Ranum, John Wiley & Sons, Inc., 1997. "Practical Unix & Internet Security", Simson Garfinkel and Gene Spafford, 2nd edition, O'Reilly and Associates, 1996. Please note that the URLs and books referenced in this advisory are not under AUSCERT's control and therefore AUSCERT cannot be responsible for their availability or content. - ---------------------------------------------------------------------------- AUSCERT thanks Muhammad Muquit for his assistance in the preparation of this advisory. - ---------------------------------------------------------------------------- The AUSCERT team have made every effort to ensure that the information contained in this document is accurate. However, the decision to use the information described is the responsibility of each user or organisation. The appropriateness of this document for an organisation or individual system should be considered before application in conjunction with local policies and procedures. AUSCERT takes no responsibility for the consequences of applying the contents of this document. If you believe that your system has been compromised, contact AUSCERT or your representative in FIRST (Forum of Incident Response and Security Teams). AUSCERT is located at The University of Queensland within the Prentice Centre. AUSCERT is a full member of the Forum of Incident Response and Security Teams (FIRST). AUSCERT maintains an anonymous FTP service which is found on: ftp://ftp.auscert.org.au/pub/. This archive contains past SERT and AUSCERT Advisories, and other computer security information. AUSCERT also maintains a World Wide Web service which is found on: http://www.auscert.org.au/. Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 4477 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 emergencies. Postal: Australian Computer Emergency Response Team Prentice Centre The University of Queensland Brisbane Qld. 4072. AUSTRALIA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision History [ End AUSCERT Advisory ] ______________________________________________________________________________ _ CIAC wishes to acknowledge the contributions of AUSCERT 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: +1 510-422-8193 FAX: +1 510-423-8002 STU-III: +1 510-423-2604 E-mail: ciac@llnl.gov For emergencies and off-hour assistance, DOE, DOE contractor sites, and the NIH may contact CIAC 24-hours a day. During off hours (5PM - 8AM PST), call the CIAC voice number 510-422-8193 and leave a message, or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC duty person, and the secondary PIN number, 8550074 is for the CIAC Project Leader. Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://ciac.llnl.gov/ Anonymous FTP: ciac.llnl.gov (198.128.39.53) Modem access: +1 (510) 423-4753 (28.8K baud) +1 (510) 423-3331 (28.8K baud) CIAC has several self-subscribing mailing lists for electronic publications: 1. CIAC-BULLETIN for Advisories, highest priority - time critical information and Bulletins, important computer security information; 2. SPI-ANNOUNCE for official news about Security Profile Inspector (SPI) software updates, new features, distribution and availability; 3. SPI-NOTES, for discussion of problems and solutions regarding the use of SPI products. Our mailing lists are managed by a public domain software package called Majordomo, which ignores E-mail header subject lines. To subscribe (add yourself) to one of our mailing lists, send the following request as the E-mail message body, substituting ciac-bulletin, spi-announce OR spi-notes for list-name: E-mail to ciac-listproc@llnl.gov or majordomo@tholia.llnl.gov: subscribe list-name e.g., subscribe bulletin You will receive an acknowledgment email immediately with a confirmation that you will need to mail back to the addresses above, as per the instructions in the email. This is a partial protection to make sure you are really the one who asked to be signed up for the list in question. If you include the word 'help' in the body of an email to the above address, it will also send back an information file on how to subscribe/unsubscribe, get past issues of CIAC bulletins via email, etc. 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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