There are two security related issues: one is a taint issue and the other has to do with not using the multi-argument version of exec to spawn programs.

First the taint problem: the value passed into $host is probably tainted and you are not untainting it. See perldoc perlsec for more info on how to untaint data.

Another security issue is your use of exec() with a single arguement. You should use something like: 

open(my $fh, "-|", $NSLOOKUP, "-type=any", $host)
  or die "unable to exec $NSLOOKUP: $!";

[download]
This ensures that $host will not be interpreted by the shell. If you really need to re-direct STDERR, consider using something like IPC::Open3.

Here is a good write-up of the security issues around tainting and calling other processes written by brian_d_foy: Secure Programming Techniques

In reply to Re: Insecure dependency in piped open by pc88mxer
in thread Insecure dependency in piped open by gugubanana

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.