FreeBSD ptrace PT_LWPINFO Denial of Service Vulnerability iDefense Security Advisory 10.10.06 http://www.idefense.com/intelligence/vulnerabilities/ Oct 10, 2006 I. BACKGROUND FreeBSD is a modern operating system for x86, amd64, Alpha, IA-64, PC-98 and SPARC architectures. It's based on the UNIX operating system, BSD, which was created at the University of California, Berkeley. More information can be obtained from the FreeBSD Project web site at http://www.FreeBSD.org/ II. DESCRIPTION The PT_LWPINFO ptrace command allows a tracer to get information on a running thread. Due to the use of signed integers and a lack of proper input validation, a situation can occur in the kernel where a panic will cause DoS. The affected code follows. 953 case PT_LWPINFO: 954 if (data == 0 || data > sizeof(*pl)) 955 return (EINVAL); Since the "data" variable is a signed integer, the check on line 954 can easily be bypassed. Eventually, the negative value is passed to copyout(), which will result in a kernel panic or corruption of the user space memory. III. ANALYSIS Exploitation of this vulnerability would result in a denial of service condition on the affected host. In some cases exploitation resulted in a hard lock up of the machine, where as other times a kernel panic was caused leading to reboot. iDefense considers this a LOW severity vulnerability due to the local access requirement. IV. DETECTION iDefense has confirmed the existence of this problem in FreeBSD version 6.0-RELEASE. FreeBSD 6.1-RELEASE is not affected. It is suspected that other versions are also affected. V. WORKAROUND iDefense is not aware of any workaround for this issue. VI. VENDOR RESPONSE "The policy of the FreeBSD Security Team is that local denial of service bugs not be treated as security issues; it is possible that this problem will be corrected in a future Erratum." VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2006-4516 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. VIII. DISCLOSURE TIMELINE 08/18/2006 Initial vendor notification 10/06/2006 Initial vendor response 10/10/2006 Public disclosure IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous. Get paid for vulnerability research http://www.idefense.com/methodology/vulnerability/vcp.php Free tools, research and upcoming events http://labs.idefense.com/ X. LEGAL NOTICES Copyright © 2006 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 email customerservice@private 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.
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