Formmail.pl Exploit - Anti-Spam and security fix available

From: kanda samy (ksamy2000at_private)
Date: Mon Jun 25 2001 - 08:24:10 PDT

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    Anti-Spam and security fix available for formmail.pl
    http://www.mailvalley.com/formmail/
    
    A serious flaw in the popular CGI program Formmail.pl
    allows spammers to send 
    anonymous emails. This vulnerability has already been
    exploited by spammers 
    in many installations of Formmail.pl.
    Reference : 
    http://www.securityfocus.com/templates/archive.pike?list=1&mid=168177
    
    Earlier, two workarounds were suggested:
    
    1) Modify the perl script to disallow the GET method
    Vulnerability of this workaround : 
    It is possible to write a script that uses POST method
    to post to formmail 
    even with a faked http_referrer field. So this may not
    be a permanent solution.
    
    2) Hard-code the recipient's address into the formmail
    perl script.
    Limitations of this workaround:
    This is not at all useful when a single formmail
    script needs to be used for multiple 
    domains and email addresses.
    
    Patched version of the Matt Wright's Formmail.pl is
    now available.
    
    Parameshwar Babu (babuwebat_private) has released
    a patched 
    version of  formmmail script that contains a fix to
    this security hole in the script. 
    The modified script allows you to specify the list of
    recipient email addresses 
    in a text file. Thus the script can be used to
    restrict emails so that they would be 
    sent only to authorized addresses.
    
    Summary :  The patched version of the script : - 
    * Prevents the script from being used by spammers 
    * Allows you to specify a list of recipients in a text
    file who are authorized to receive emails. 
    * Prevents unauthorised users from fetching your
    server's environment variables. 
    * Can be used by web-hosting providers, webmasters and
    anyone who needs to use 
    the same formmail script to several webpages or
    domains. 
    
    Another exploit was reported which makes it possible
    for a remote user to view the 
    Environment and Setup variables of the server running
    the formmail perl script. 
    Reference : 
    http://www.securityfocus.com/templates/archive.pike?list=1&mid=59441
    
    The patched script mentioned here also prevents an
    unauthorised user from 
    fetching the environment and setup variables of the
    server. 
    
    A patched version of the script can be downloaded from
    http://www.mailvalley.com/formmail/
    
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