Public Vulnerability Reports

WU-FTPD File Globbing Denial of Service Vulnerability



WU-FTPD is an ftp daemon for Unix systems developed at Washington
University. More information is available at:


Remote exploitation of an input validation vulnerability in version
2.6.2 of WU-FPTD could allow for a denial of service of the system by
resource exhaustion.

The vulnerability specifically exists in the wu_fnmatch() function in
wu_fnmatch.c. When a pattern containing a '*' character is supplied as
input, the function calls itself recursively on a smaller substring. By
supplying a string which contains a large number of '*' characters, the
system will take a long time to return the results, during which time it
will be using a large amount of CPU time.


After a user logs into the ftpd, an attacker can send a simple command
which will cause high CPU utilization.

To exploit this vulnerability, a simple ftp client is sufficient. Once
logged  in, either anonymously or as an authenticated user, issuing the
following command will cause the machine to become less responsive.

ftp> dir ***************************************************************

By re-connecting and issuing the command multiple times, the system can
be made completely unresponsive. This may prevent legitimate access to
services provided by the system for the period of the attack.


iDEFENSE has confirmed the existence of this vulnerability in version
2.6.2 and 2.6.1 of WU-FTPD. It is suspected that previous versions are
also affected by this vulnerability.


Consider disabling the ftpd. If this is not viable as an option,
consider disabling anonymous access. Disabling anonymous access will not
prevent local users from exploiting this vulnerability.


No vendor response received.


The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0256 to these issues. This is a candidate for inclusion
in the CVE list (, which standardizes names for
security problems.


02/09/2005   Initial vendor notification - No response
02/18/2005   Initial vendor notification - No response
02/25/2005   Public disclosure


Adam Zabrocki (pi3 / pi3ki31ny) is credited with this discovery.

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Copyright © 2005 Verisign, Inc.

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