Bugtraq: [HSC] Multiple transversal bug in vis

[spher3 () hackerscenter com]

Hackers Center Security Group (http://www.hackerscenter.com/) 
spher3's Security Advisory 

Multiple transversal bug in vis.pl 


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Description: 

Vis.pl is a perl script which manages files in order to show these; 
you can find it in e-cms default files. The vulnerability taken in 
exam is classifiable as transversal bug. In fact can show to everybody 
files such as passwords or accounts. 

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Code Details: 

Vis.pl doesn't control cgi query except for: 

[...] 

if ( -e $datFile ) 
{ 
open ( DAT_FILE, "$datFile" ); 

[...] 

This function controls only the file existence. 
Then the script start to open the file without check dangerous 
characters as "." and "/". 
So is simply to access where you want: 

http://[target]/cgi-bin/e-cms/vis/vis.pl?s=001&p=../../../../etc/passwd%00 

All variables that open files are unsafe: 

http://[target]/cgi-bin/e-cms/vis/vis.pl?s=../../../../etc/passwd%00 

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How to fix: 

You can fix this script with remove those dangerouse characters as taught 
from W3C WWW Security FAQ. Just adding a line: 

$datFile = s/\.\.//g; 

You have to insert a line like this for ALL variables which contain files 
to open.