__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN NFS mountd Buffer Overflow Vulnerability October 26, 1998 22:00 GMT Number J-006 ______________________________________________________________________________ PROBLEM: There is a vulnerability in some implementations of the software that NFS servers use to log request to file systems. PLATFORM: NFS servers, primarily Linux systems. DAMAGE: If exploited, a remote intruder may cause a buffer overflow which can lead to root access. SOLUTION: Apply patches or workaround. ______________________________________________________________________________ VULNERABILITY Risk is high. This exploit is available on the Internet and ASSESSMENT: can cause a total system compromise. ______________________________________________________________________________ [ Appended on October 26, 1998 with additional patch information from Silicon Graphics Inc. ] [ Start CERT Advisory ] ========================================================================== CERT* Advisory CA-98.12 Original issue date: October 12, 1998 A complete revision history is at the end of this file. Topic: Remotely Exploitable Buffer Overflow Vulnerability in mountd - ------------------------------------------------------------------------- Affected systems: NFS servers running certain implementations of mountd, primarily Linux systems. On some systems, the vulnerable NFS server is enabled by default. This vulnerability can be exploited even if the NFS server does not share any file systems. See Appendix A for information from vendors. If your vendor's name does not appear, we did not hear from that vendor. Overview: NFS is a distributed file system in which clients make use of file systems provided by servers. There is a vulnerability in some implementations of the software that NFS servers use to log requests to use file systems. When a client makes a request to use a file system and subsequently makes that file system available as a local resource, the client is said to "mount" the file system. The vulnerability lies in the software on the NFS server that handles requests to mount file systems. This software is usually called "mountd" or "rpc.mountd." Intruders who exploit the vulnerability are able to gain administrative access to the vulnerable NFS file server. That is, they can do anything the system administrator can do. This vulnerability can be exploited remotely and does not require an account on the target machine. On some vulnerable systems, the mountd software is installed and enabled by default. See Appendix A for more information. We will update this advisory as we receive additional information. Please check our advisory files regularly for updates that relate to your site. - ------------------------------------------------------------------------- I. Description NFS is used to share files among different computers over the network using a client/server paradigm. When an NFS client computer wishes to access files on an NFS server, the client must first make a request to mount the file system. There is a vulnerability in some implementations of the software that handles NFS mount requests (the mountd program). Specifically, it is possible for an intruder to overflow a buffer in the area of code responsible for logging NFS activity. We have received reports indicating that intruders are actively using this vulnerability to compromise systems and are engaging in large-scale scans to locate vulnerable systems. On some systems, the vulnerable NFS server is enabled by default. See the vendor information in Appendix A. II. Impact After causing a buffer overflow, a remote intruder can use the resulting condition to execute arbitrary code with root privileges. III. Solution A. Install a patch from your vendor. Appendix A contains input from vendors who have provided information for this advisory. We will update the appendix as we receive more information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact your vendor directly. B. Until you install a patch, use the following workaround. Consider disabling NFS until you are able to install the patch. In particular, since some systems have vulnerable versions of mountd installed and enabled by default, we recommend you disable mountd on those systems unless you are actively using those systems as NFS servers. - ------------------------------------------------------------------------- Appendix A - Vendor Information Below is a list of the vendors who have provided information for this advisory. We will update this appendix as we receive additional information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact the vendor directly. Caldera ======= Caldera provided a fixed version as nfs-server-2.2beta35-2 on Aug 28. It is available from ftp://ftp.caldera.com/pub/OpenLinux/updates/1.2/013 10fdb82ed8fd1b88c73fd962d8980bb4 RPMS/nfs-server-2.2beta35-2.i386.rpm 59e275b1ed6b98a39a38406f0415a226 RPMS/nfs-server-clients-2.2beta35-2.i386.rpm 6b075faf1d424e099c6932d95e76fd6b SRPMS/nfs-server-2.2beta35-2.src.rpm Compaq Computer Corporation =========================== SOURCE: (c) Copyright 1994, 1995, 1996, 1997, 1998 Compaq Computer Corporation. All rights reserved. SOURCE: Compaq Computer Corporation Compaq Services Software Security Response Team USA x-ref: SSRT0574U mountd This reported problem is not present for the as shipped, Compaq's Digital ULTRIX or Compaq's Digital UNIX Operating Systems Software. - - - Compaq Computer Corporation Data General Corporation ======================== We are investigating. We will provide an update when our investigation is complete. FreeBSD, Inc. ============= FreeBSD 2.2.6 and above seem not be vulnerable to this exploit. Fujitsu Limited =============== Fujitsu's UXP/V operating system is not vulnerable. Hewlett-Packard Company ======================= Not vulnerable. NCR === NCR is not vulnerable. We do not do any of the specified logging, nor do we have mountd (or normally anything else) hanging on port 635. The NetBSD Project ================== NetBSD is not vulnerable to this attack in any configuration. Neither the NFS server or mount daemon are enabled by default. The OpenBSD Project =================== OpenBSD is not affected. Red Hat Software, Inc. ====================== All versions of Red Hat Linux are vulnerable, and we have provided fixed packages for all our users. Updated nfs-server packages are available from our site at http://www.redhat.com/support/docs/errata.html The Santa Cruz Operation, Inc. ============================== No SCO platforms are vulnerable. Sun Microsystems, Inc. ====================== Sun's mountd is not affected. - ------------------------------------------------------------------------- Contributors Our thanks to Olaf Kirch and Wolfgang Ley for their input and assistance in constructing this advisory. - ------------------------------------------------------------------------- [ End CERT Advisory ] [ Append Silicon Graphics Advisory ] -----BEGIN PGP SIGNED MESSAGE----- ______________________________________________________________________________ Silicon Graphics Inc. Security Advisory Title: mountd Buffer Overflow Vulnerability Title: CERT* Advisory CA-98.12 Number: 19981006-01-I Date: October 26, 1998 ______________________________________________________________________________ Silicon Graphics provides this information freely to the SGI user community for its consideration, interpretation, implementation and use. Silicon Graphics recommends that this information be acted upon as soon as possible. Silicon Graphics provides the information in this Security Advisory on an "AS-IS" basis only, and disclaims all warranties with respect thereto, express, implied or otherwise, including, without limitation, any warranty of merchantability or fitness for a particular purpose. In no event shall Silicon Graphics be liable for any loss of profits, loss of business, loss of data or for any indirect, special, exemplary, incidental or consequential damages of any kind arising from your use of, failure to use or improper use of any of the instructions or information in this Security Advisory. ______________________________________________________________________________ As a followup to CERT(sm) Advisory CA-98.12 "Remotely Exploitable Buffer Overflow Vulnerability in mountd", SGI has investigated this issue and provides the following information. - ----------------------- - --- Issue Specifics --- - ----------------------- The mountd program is a server process that coordinates filesystem mount requests. A buffer overflow vulnerability has been discovered in the mountd program that can allow root access according to CERT(sm) Advisory CA-98.12. Silicon Graphics Inc. has investigated the issue and finds all versions of IRIX, Unicos and Unicos/mk are not vulnerable to this issue and no further action is required. - ------------------------ - --- Acknowledgments --- - ------------------------ Silicon Graphics wishes to thank the CERT Coordination Center and the users of the Internet Community at large for their assistance in this matter. - ----------------------------------------------------------- - --- Silicon Graphics Inc. Security Information/Contacts --- - ----------------------------------------------------------- If there are questions about this document, email can be sent to cse-security-alert@sgi.com. ------oOo------ Silicon Graphics provides security information and patches for use by the entire SGI community. This information is freely available to any person needing the information and is available via anonymous FTP and the Web. The primary SGI anonymous FTP site for security information and patches is sgigate.sgi.com (204.94.209.1). Security information and patches are located under the directories ~ftp/security and ~ftp/patches, respectively. The Silicon Graphics Security Headquarters Web page is accessible at the URL http://www.sgi.com/Support/security/security.html. For issues with the patches on the FTP sites, email can be sent to cse-security-alert@sgi.com. For assistance obtaining or working with security patches, please contact your SGI support provider. ------oOo------ Silicon Graphics provides a free security mailing list service called wiretap and encourages interested parties to self-subscribe to receive (via email) all SGI Security Advisories when they are released. Subscribing to the mailing list can be done via the Web (http://www.sgi.com/Support/security/wiretap.html) or by sending email to SGI as outlined below. % mail wiretap-request@sgi.com subscribe wiretap end ^d In the example above, is the email address that you wish the mailing list information sent to. The word end must be on a separate line to indicate the end of the body of the message. The control-d (^d) is used to indicate to the mail program that you are finished composing the mail message. ------oOo------ Silicon Graphics provides a comprehensive customer World Wide Web site. This site is located at http://www.sgi.com/Support/security/security.html. ------oOo------ For reporting *NEW* SGI security issues, email can be sent to security-alert@sgi.com or contact your SGI support provider. A support contract is not required for submitting a security report. ______________________________________________________________________________ This information is provided freely to all interested parties and may be redistributed provided that it is not altered in any way, Silicon Graphics is appropriately credited and the document retains and includes its valid PGP signature. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBNjT7lLQ4cFApAP75AQE9ugQAhu/xqzO9n30GuAMos6wzT/33YbUeBKy7 5PFpan5hMeTCyjJoGPYTJckIttIiuPa21V2n28NEkfd2eKFV4yYt++fe6bBzfKij Ub7S/Ve9YgDgTxbivOJTF+y3vfCdyTB0DE0uW0ZyqQsE6j4JmECRHiFKy6VJo5Ky CmlFo/Zg3Nc= =EsF5 -----END PGP SIGNATURE----- [ End Silicon Graphics Advisory ] ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of CERT 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). 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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. LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) I-088: NFS clients rpc.pcnfsd Vulnerability I-089: SGI Seyon Security Vulnerability I-090: HP-UX dtmail/rpc.ttdbserverd Vulnerability I-091: Stack Overflow in ToolTalk RPC Service I-092: Ping Buffer Overflow Vulnerability J-001: Windows NT RPC Spoofing Denial of Service Vulnerability J-002: SGI IRIX Mail(1)/mailx(1) Security Vulnerabilities J-003: SGI IRIX On-Line Customer Registration Vulnerabilities J-004: SunOS ftp client Vulnerability J-005: SGI IRIX at(1) Vulnerability