Vulnerability Note VU#210409

Multiple FTP clients contain directory traversal vulnerabilities

Overview

Multiple File Transfer Protocol (FTP) clients contain directory traversal vulnerabilities that allow a malicious FTP server to overwrite files on the client host.

I. Description

In a typical file transfer operation, one participant (the client) requests a file while a second participant (the server) provides the requested file. Before processing each request, many server implementations will consult an access control policy to determine whether the client should be permitted to read, write, or create a file at the requested location. If the client is able to craft a request that violates the server's access control policy, then the server contains a vulnerability. Since most vulnerabilities of this type involve escaping a restricted set of directories, they are commonly known as "directory traversal" vulnerabilities.

Directory traversal vulnerabilities are most often reported in server implementations, but recent research into the behavior of FTP clients has revealed several vulnerabilities in various FTP client implementations. To exploit these vulnerabilities, an attacker must convince the FTP client user to access a specific FTP server containing files with crafted filenames. When an affected FTP client attempts to download one of these files, the crafted filename causes the client to write the downloaded files to the location specified by the filename, not by the victim user. In some cases, the attacker must use a modified FTP server to allow the crafted filenames to be passed to the client.

For more detailed information regarding this research, please read "Directory Traversal Vulnerabilities in FTP Clients", written by Steve Christey.

II. Impact

This vulnerability allows an attacker to mislead users of affected FTP clients, convincing the victim to unintentionally create or overwrite files on the client's filesystem.

III. Solution

Apply a patch from your vendor

For vendor-specific information regarding vulnerability status and patch availability, please consult the Systems Affected section of this document

Systems Affected

Vendor	Status	Date Notified
Apple Computer Inc.	Unknown	5-Dec-2002
BSDI	Unknown	5-Dec-2002
Cray Inc.	Unknown	5-Dec-2002
Data General	Unknown	5-Dec-2002
F5 Networks	Unknown	5-Dec-2002
FreeBSD	Unknown	5-Dec-2002
Fujitsu	Unknown	5-Dec-2002
Guardian Digital Inc.	Unknown	5-Dec-2002
Hewlett-Packard Company	Unknown	5-Dec-2002
IBM	Not Vulnerable	19-Dec-2002
Juniper Networks	Unknown	5-Dec-2002
Microsoft Corporation	Unknown	5-Dec-2002
MontaVista Software	Unknown	5-Dec-2002
NcFTP Software	Vulnerable	19-Dec-2002
NEC Corporation	Unknown	5-Dec-2002
NetBSD	Unknown	5-Dec-2002
Nokia	Unknown	5-Dec-2002
OpenBSD	Unknown	5-Dec-2002
Openwall GNU/*/Linux	Not Vulnerable	9-Dec-2002
publicfile	Unknown	19-Dec-2002
Sequent	Unknown	5-Dec-2002
SGI	Unknown	19-Dec-2002
Sony Corporation	Unknown	5-Dec-2002
Sun Microsystems Inc.	Vulnerable	9-Dec-2002
SuSE Inc.	Unknown	5-Dec-2002
The SCO Group (SCO Linux)	Unknown	5-Dec-2002
The SCO Group (SCO UnixWare)	Unknown	5-Dec-2002
Unisys	Unknown	5-Dec-2002
Wind River Systems Inc.	Unknown	5-Dec-2002
Wirex	Unknown	5-Dec-2002
WU-FTPD Development Group	Unknown	5-Dec-2002

References

http://online.securityfocus.com/archive/1/302956

Credit

The CERT/CC thanks Steve Christey for his discovery and analysis of these vulnerabilities.

This document was written by Jeffrey P. Lanza.

Other Information

Date Public:	2002-12-10
Date First Published:	2002-12-10
Date Last Updated:	2003-03-14
CERT Advisory:
CVE-ID(s):	CAN-2002-1345
NVD-ID(s):	CAN-2002-1345
US-CERT Technical Alerts:
Metric:	2.81
Document Revision:	31

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