iDefense Security Advisory 10.07.09 http://labs.idefense.com/intelligence/vulnerabilities/ Oct 07, 2009 I. BACKGROUND IBM's AIX is a Unix operating system based on System V, which runs on the PowerPC (PPC) architecture. For more information, visit the product web site at the following URL. http://www.ibm.com/systems/power/software/aix/index.html II. DESCRIPTION Remote exploitation of a stack based buffer overflow vulnerability in IBM Corp.'s AIX could allow an attacker to execute arbitrary code with the privileges of the affected service. rpc.cmsd, more commonly known as the Calendar Manager Service Daemon, is an RPC application used to manage schedules and calendars. It operates over SUN RPC. The vulnerability is triggered when handling a request for remote procedure 21. This function takes two arguments, both of which are XDR strings. When copying the first argument into a stack based buffer, the code does not properly verify its length. This results in a stack based buffer overflow vulnerability. III. ANALYSIS Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the affected service, usually root. In order to exploit this vulnerability, an attacker only needs the ability to connect to the target host via RPC. No authentication is required. Since the vulnerability is a stack based buffer overflow, exploitation is relatively trivial. IV. DETECTION iDefense has confirmed the existence of this vulnerability in AIX versions 5.3 and 5.2. IBM reports that this vulnerability is present in the following products: AIX 5.3, 6.1, and earlier releases VIOS 1.4, 1.5, 2.1, and earlier releases V. WORKAROUND Disabling the cmsd RPC service via inetd.conf will prevent the exploitation of this vulnerability. This can be performed using the 'chsubserver' command, and is documented in the AIX advisory linked to below. However, this will prevent users from using the Calendar/Scheduler service. VI. VENDOR RESPONSE IBM has addressed this issue with an update. Further details and patches can be found at the following URLs. http://aix.software.ibm.com/aix/efixes/security/cmsd_advisory.asc http://aix.software.ibm.com/aix/efixes/security/cmsd_fix.tar VII. CVE INFORMATION A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet. VIII. DISCLOSURE TIMELINE 08/25/2009 Initial vendor notification 08/25/2009 Initial vendor response 10/07/2009 Public disclosure IX. CREDIT This vulnerability was reported to iDefense by Rodrigo Rubira Branco (BSDaemon). Get paid for vulnerability research http://labs.idefense.com/methodology/vulnerability/vcp.php Free tools, research and upcoming events http://labs.idefense.com/ X. LEGAL NOTICES Copyright © 2009 iDefense, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDefense. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please e-mail customerservice@idefense.com for permission. Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information. _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/