Vulnerability Note VU#246409

CGI.pm vulnerable to Cross-site Scripting

Overview

A vulnerability in the Common Gateway Interface (CGI) Perl module may allow an attacker to mount a cross-site scripting attack against a vulnerable system.

I. Description

The Common Gateway Interface, or CGI, is a standard for external gateway programs to interface with information servers such as HTTP servers. The standard Perl distribution and many vendor's repackaged Perl systems include a CGI library known as CGI.pm. This module offers a set of functions for creating fill-out forms, among other things.

Some versions of the CGI.pm module contain a vulnerability in handling of the action in the start_form() and start_multipart_form() functions. When the action for the form is not specified, a default based on the user-supplied URL is used. Because the value of this expression is not sanitized by the module before processing and contains user-supplied data or data received from untrustworthy sources, a remote attacker may be able to inject HTML or malicious script. A user of the vulnerable site or web application may then be tricked into interpreting the HTML or executing the script in a situation where they normally might not.

II. Impact

The victim will be presented with information that the vulnerable site did not wish their visitors to be subjected to. This could be used to "sniff" sensitive data from within the web page, including passwords, credit card numbers, and any arbitrary information the user inputs. This exploitation vector is commonly referred to as a cross-site scripting attack.

III. Solution

Apply a patch from the vendor

Versions 2.94 and later of the CGI.pm module contain a fix for this vulnerability. Please see the vendor section of this document for further details.

Systems Affected

Vendor	Status	Date Notified
Conectiva	Vulnerable	30-Jul-2003
Debian	Vulnerable	21-Aug-2003
Lincoln Stein	Vulnerable	7-Oct-2003
MandrakeSoft	Vulnerable	2-Sep-2003
OpenBSD	Vulnerable	2-Sep-2003
OpenPKG	Vulnerable	7-Oct-2003
Red Hat Inc.	Vulnerable	7-Oct-2003
SCO	Vulnerable	13-Nov-2003
Sun Microsystems Inc.	Vulnerable	11-Feb-2004

References

http://stein.cshl.org/WWW/software/CGI/
http://eyeonsecurity.org/advisories/
http://xforce.iss.net/xforce/xfdb/12669

Credit

Thanks to Obscure for reporting this vulnerability.

This document was written by Chad R Dougherty with feedback from Sean Levy.

Other Information

Date Public:	2003-07-19
Date First Published:	2003-10-07
Date Last Updated:	2004-02-23
CERT Advisory:
CVE-ID(s):	CAN-2003-0615
NVD-ID(s):	CAN-2003-0615
US-CERT Technical Alerts:
Metric:	15.00
Document Revision:	10

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