Security Bulletin 9506 DISA Defense Communications System February 15, 1995 Published by: DDN Security Coordination Center (SCC@NIC.DDN.MIL) 1-(800) 365-3642 DEFENSE DATA NETWORK SECURITY BULLETIN The DDN SECURITY BULLETIN is distributed by the DDN SCC (Security Coordination Center) under DISA contract as a means of communicating information on network and host security exposures, fixes, and concerns to security and management personnel at DDN facilities. Back issues may be obtained via FTP (or Kermit) from NIC.DDN.MIL [192.112.36.5] using login="anonymous" and password="guest". The bulletin pathname is scc/ddn-security-yynn (where "yy" is the year the bulletin is issued and "nn" is a bulletin number, e.g. scc/ddn-security-9505). ************************************************************************** + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + | The following important advisory was issued by the Department of | | Energy's Computer Incident Advisory Capability (CIAC), and is being | | relayed unedited via the Defense Information Systems Agency's | | Security Coordination Center distribution system as a means | | of providing DDN subscribers with useful security information. | + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + _____________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ _____________________________________________________ ADVISORY NOTICE Unix NCSA httpd Vulnerability February 14, 1995 1030 PST Number F-11 _____________________________________________________________________________ PROBLEM: A vulnerability has been discovered in the NCSA WWW server software (httpd). PLATFORMS: Unix systems running NCSA httpd version 1.3. DAMAGE: Remote users may gain unauthorized access. SOLUTION: Implement workaround as described below. _____________________________________________________________________________ VULNERABILITY This vulnerability, along with an automated exploitation ASSESSMENT: script, has been announced in public forums on the Internet. CIAC recommends that sites install the workaround on affected systems as soon as possible. _____________________________________________________________________________ Critical Information about the NCSA httpd Vulnerability CIAC has learned of a serious vulnerability in the NCSA WWW server software, httpd. By sending a carefully constructed request to the WWW server, an intruder can cause an internal buffer overflow and push arbitrary instructions onto the program stack. These new instructions may allow the intruder unauthorized access to the WWW server. Until official patches are available from NCSA, CIAC recommends the following temporary fix be installed. In the file httpd.h, change the string length definitions from: /* The default string lengths */ #define MAX_STRING_LEN 256 #define HUGE_STRING_LEN 8192 to: /* The default string lengths */ #define HUGE_STRING_LEN 8192 #define MAX_STRING_LEN HUGE_STRING_LEN Then rebuild, install, and restart the new httpd server. It is likely that these attacks will generate unusual server log entries. The httpd access_log file should be examined for unusual requests, especially those containing control characters. Note that while this workaround addresses the vulnerability currently being exploited, there are likely to be other similar vulnerabilities present in this and other WWW server software. To lessen the chance of compromise, it is strongly recommended that WWW servers run as unprivileged users (e.g. user "nobody") and that they be locked into a restricted filesystem via the chroot() system call. For more information, please see CIAC Document 2308, "Securing Internet Information Servers," which is available via anonymous FTP from ciac.llnl.gov in the directory /pub/ciac/ciacdocs/. _____________________________________________________________________________ CIAC wishes to acknowledge the contributions of the DFN-CERT in the construction of this bulletin. _____________________________________________________________________________ For emergencies and off-hour assistance, DOE and DOE contractor sites can contact CIAC 24-hours a day via an integrated voicemail and SKYPAGE number. To use this service, dial 1-510-422-8193 or 1-800-759-7243 (SKYPAGE). The primary SKYPAGE PIN number, 8550070 is for the CIAC duty person. A second PIN, 8550074 is for the CIAC Project Leader. CIAC's FAX number is 510-423-8002, and the STU-III number is 510-423-2604. Send E-mail to ciac@llnl.gov. Previous CIAC notices, anti-virus software, and other information are available on the Internet via anonymous FTP from ciac.llnl.gov (IP address 128.115.19.53). 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. CIAC-NOTES for Notes, a collection of computer security articles; 3. SPI-ANNOUNCE for official news about Security Profile Inspector (SPI) software updates, new features, distribution and availability; 4. 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 ListProcessor, which ignores E-mail header subject lines. To subscribe (add yourself) to one of our mailing lists, send requests of the following form: subscribe list-name LastName, FirstName PhoneNumber as the E-mail message body, substituting CIAC-BULLETIN, CIAC-NOTES, SPI-ANNOUNCE or SPI-NOTES for "list-name" and valid information for "LastName" "FirstName" and "PhoneNumber." Send to: ciac-listproc@llnl.gov not to: ciac@llnl.gov e.g., subscribe ciac-notes O'Hara, Scarlett 404-555-1212 x36 subscribe ciac-bulletin O'Hara, Scarlett 404-555-1212 x36 You will receive an acknowledgment containing address and initial PIN, and information on how to change either of them, cancel your subscription, or get help. _____________________________________________________________________________ PLEASE NOTE: Many users outside of the DOE and ESnet 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 by sending E-mail to first-request@first.org with an empty subject line and a message body containing the line: send first-contacts. 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, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, 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 nor the University of California, and shall not be used for advertising or product endorsement purposes. **************************************************************************** * * * The point of contact for MILNET security-related incidents is the * * Security Coordination Center (SCC). * * * * E-mail address: SCC@NIC.DDN.MIL * * * * Telephone: 1-(800)-365-3642 * * * * NIC Help Desk personnel are available from 7:00 a.m.-7:00 p.m. EST, * * Monday through Friday except on federal holidays. * * * **************************************************************************** PLEASE NOTE: Some users outside of the DOD computing communities may receive DDN Security bulletins. If you are not part of the DOD community, please contact your agency's incident response team to report incidents. Your agency's team will coordinate with DOD. 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 by sending email to docserver@first.org with an empty subject line and a message body containing the line: send first-contacts. This document was prepared as an service to the DOD community. Neither the United States Government nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, 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. The opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government, and shall not be used for advertising or product endorsement purposes.