Rule:

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Sid:
1610

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Summary:
An attempt to access a script (formmail) in the cgi-bin which has known
vulnerabilities.

Formmail is a freely available perl script that is used to send data
collected via a form to specified addresses.

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Impact:
Attempt to gain information about the web-server environment variables.
Could also be an attempt to execute commands on the web-server that will
execute with the privilege of the user owning the daemon running the
server. The script may also be used to relay SPAM or to disclose the
contents of files on the host.

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Detailed Information:
This could be an attempt to gain intelligence about the web-server that
might be used to further exploit the machine. The environment variables
of the web-server might be retrieved and sent via email to an address of
the attackers choosing. More importantly this could be an attempt to
execute commands on the web-server. Should this be successful, the
commands would execute with the privileges of the user owning the httpd daemon.

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Attack Scenarios:
Formmail receives information from a form via an HTTP POST. This
includes the email addresses to which the form data is sent. A URI in
the form of a POST to the formmail script could be crafted to send
environment variables to a specified email address.

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Ease of Attack:
Simple. Exploit software is not required.

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False Positives:
None known.

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False Negatives:
None Known

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Corrective Action:
Web-servers should not be allowed to view or execute files and binaries
outside of it's designated web root or cgi-bin. The web-server httpd
daemon should be run as a non-privileged user without login access to
the host. The formmail script should be updated to a non-vulnerable
version as soon as possible.

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Contributors:
Sourcefire Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

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