Rule:  

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Sid:
882

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Summary: 
This event is generated when an attempt is made to access a web 
application that may lead to exploitation of the application.

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Impact: 
Potentially harmful execution of binaries through perl open()

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Detailed Information: 
An open source calendar perl script by Matt Kruse, Allows commands to be executed without input verification using the perl open() function. ie /cgi-bin/calendar_admin.pl place the string "|ping 127.0.0.1|" in the configuration file field, this executes the command "ping 127.0.0.1" 

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Affected Systems:
Any web server running the application.

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Attack Scenarios: 
An unauthenticated user can execute arbitrary programs on the server by accessing calendar_admin.pl and inputting commands such as "|mail /etc/passwd|" into the configuration file field.

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Ease of Attack: 
Simple. No exploit software required.

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False Positives: 
If your webserver has pages by the name of calendar* this rule will
fire often. Many sites now use calendar applications and this rule may 
generate a large number of false positives, it does not distinguish 
between perl cgi applications and php scripts. Consider tuning this rule
for your site if it is generating a large number of false positives. If 
you use a calendar application, consider changing the name of the script
to something other than "calendar".

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False Negatives: 
None known.

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Corrective Action: 
Download a newer version of the cgi 

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Contributors: 
Original Rule Writer Unknown
Snort documentation contributed by Aaron Navratil (Initial Research)
Snort documentation contributed by Josh Gray (Edits)
Sourcefire Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

CVE:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-0432

Bugtraq:
http://online.securityfocus.com/bid/1215

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