CERT® Advisory CA-99-05 Vulnerability in statd exposes vulnerability in automountdOriginal issue date: June 9, 1999
Last revised: November 9, 1999
Added Vendor information for IBM Corporation.
Systems running older versions of rpc.statd and automountd
This advisory describes two vulnerabilities that are being used together by intruders to gain access to vulnerable systems. The first vulnerability is in rpc.statd, a program used to communicate state changes among NFS clients and servers. The second vulnerability is in automountd, a program used to automatically mount certain types of file systems. Both of these vulnerabilities have been widely discussed on public forums, such as BugTraq, and some vendors have issued security advisories related to the problems discussed here. Because of the number of incident reports we have received, however, we are releasing this advisory to call attention to these problems so that system and network administrators who have not addressed these problems do so immediately. For more information about attacks using various RPC services please see CERT® Incident Note IN-99-04 http://www.cert.org/incident_notes/IN-99-04.html
The vulnerability in rpc.statd allows an intruder to call arbitrary rpc services with the privileges of the rpc.statd process. The called rpc service may be a local service on the same machine or it may be a network service on another machine. Although the form of the call is constrained by rpc.statd, if the call is acceptable to another rpc service, the other rpc service will act on the call as if it were an authentic call from the rpc.statd process.
The vulnerability in automountd allows a local intruder to execute arbitrary commands with the privileges of the automountd process. This vulnerability has been widely known for a significant period of time, and patches have been available from vendors, but many systems remain vulnerable because their administrators have not yet applied the appropriate patches.
By exploiting these two vulnerabilities simultaneously, a remote intruder is able to "bounce" rpc calls from the rpc.statd service to the automountd service on the same targeted machine. Although on many systems the automountd service does not normally accept traffic from the network, this combination of vulnerabilities allows a remote intruder to execute arbitrary commands with the administrative privileges of the automountd service, typically root.
The vulnerability in rpc.statd may allow a remote intruder to call arbitrary rpc services with the privileges of the rpc.statd process, typically root. The vulnerablility in automountd may allow a local intruder to execute arbitrary commands with the privileges of the automountd service.
By combining attacks exploiting these two vulnerabilities, a remote intruder is able to execute arbitrary commands with the privileges of the automountd service.
It may still be possible to cause rpc.statd to call other rpc services even after applying patches which reduce the privileges of rpc.statd. If there are additional vulnerabilities in other rpc services (including services you have written), an intruder may be able to exploit those vulnerabilities through rpc.statd. At the present time, we are unaware of any such vulnerabilitity that may be exploited through this mechanism.
III. SolutionsInstall 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.
Appendix A: Vendor InformationCaldera
Silicon Graphics, Inc.
Our thanks to Olaf Kirch of Caldera for his assistance in helping us understand the problem and Chok Poh of Sun Microsystems for his assistance in helping us construct this advisory.
This document is available from: http://www.cert.org/advisories/CA-99-05-statd-automountd.html
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Copyright 1999 Carnegie Mellon University.
October 22, 1999 Updated vendor information for Hewlett-Packard Company July 22, 1999 Added link to IN-99-04 in the "Description" section. November 9, 1999 Added vendor information for IBM Corporation.