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IBM AIX ftp domacro Parameter Buffer Overflow Vulnerability

10.30.07

BACKGROUND

The ftp program is a client application for accessing data stored on FTP servers. This client is responsible for interfacing with users and speaking the FTP protocol with remote servers. Under AIX, the ftp program is installed by default and is set-uid root. More information can be found at the URL shown below.

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/topic/com.ibm.aix.cmds/doc/aixcmds2/ftp.htm

DESCRIPTION

Local exploitation of a buffer overflow vulnerability in the ftp client of IBM Corp.'s AIX operating system allows attackers to execute arbitrary code with root privileges.

The problem specifically exists within the domacro() function. This function is called when executing a macro via the '$' command within the ftp program. When executing a macro, the parameter is copied to a fixed size stack buffer using an unbounded call to strcpy(). By specifying a long argument, an attacker is able to overwrite program control data located on the stack and take control of the affected process.

ANALYSIS

Exploitation allows an attacker to execute arbitrary code with root privileges. Local access is required to execute and interact with the ftp program.

DETECTION

iDefense has confirmed the existence of this vulnerability in AIX version 5.3 (5300-06). Previous versions are suspected to be vulnerable.

WORKAROUND

Removing the set-uid bit from the ftp program will protect against exploitation. However, doing so will render the program unusable.

VENDOR RESPONSE

IBM Corp. has addressed this vulnerability by releasing interim fixes. More information can be found via the Bulletins tab of IBM's Subscription Service for UNIX and Linux servers. You can reach this service by clicking the URL shown below.

http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd?mode=1

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-4217 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

08/15/2007 Initial vendor notification
08/15/2007 Initial vendor response
10/30/2007 Coordinated public disclosure

CREDIT

This vulnerability was discovered by Joshua J. Drake of VeriSign iDefense Labs.

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LEGAL NOTICES

Copyright © 2007 Verisign, Inc.

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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.