Vulnerability Note VU#496064

ibrow NewsDesk does not securely handle input passed to open()

Overview

A vulnerability in ibrow NewsDesk allows an attacker to view files and execute operating system commands with the privileges of the web server.

I. Description

ibrow NewsDesk is a Perl CGI script that is designed to create and display news articles on a web site. The code for NewsDesk is implemented in the file newsdesk.cgi. This code accepts input from a URL and uses this data in an argument to the Perl open() command. Since NewsDesk does not adequately filter URL input, it is possible to construct a URL containing shell meta-characters such as "../" and "|" (pipe), and these characters will be processed with the privileges of the web server.

II. Impact

By submitting a specially crafted URL, an attacker can execute operating system commands and traverse the file system and read files with the permission of the web server.

III. Solution

The CERT/CC is currently unaware of a practical solution to this problem.

Modify NewsDesk

Modify newsdesk.cgi to only allow acceptable characters in URL input that is passed to open(). This type of input validation is referred to as "positive" or "whitelist" filtering. See Laundering and Detecting Tainted Data in perlsec for more information.
Enabling Perl "taint" checking will prevent execution of commands using the pipe character ("|"). See perlsec and the Secure Programming for Linux and Unix HOWTO for more information.
Rewrite the vulnerable open() calls in newsdesk.cgi to be safer, possibly by using sysopen(). See perlopentut for more information.

Systems Affected

Vendor	Status	Date Notified	Date Updated
ibrow	Vulnerable	2-Apr-2002

References

http://www.securityfocus.com/bid/2172
http://www.iss.net/security_center/static/5898.php
http://www.safermag.com/html/safer33/alerts/92.html
http://www.secureroot.com/security/advisories/9786224444.html
http://www.eeye.com/html/Support/Retina/RTHs/CGI_Scripts/560.html
http://www.perldoc.com/perl5.6/pod/func/open.html
http://www.perldoc.com/perl5.6/pod/perlopentut.html
http://www.perldoc.com/perl5.6.1/pod/perlsec.html
http://www.linuxdoc.org/HOWTO/Secure-Programs-HOWTO/perl.html

Credit

The CERT Coordination Center acknowledges <path@ns.sympatico.ca> as the reporter of this vulnerability.

This document was written by Art Manion.

Other Information

Date Public:	2001-01-04
Date First Published:	2002-04-02
Date Last Updated:	2002-04-08
CERT Advisory:
CVE-ID(s):	CAN-2001-0231
NVD-ID(s):	CAN-2001-0231
US-CERT Technical Alerts:
Metric:	2.97
Document Revision:	22

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