Products: Cpanel 5 and below (http://www.cpanel.net)
Date: 19th February 2003
Author: pokleyzz <pokleyzz_at_scan-associates.net>
Contributors: sk <sk_at_scan-associates.net>
shaharil <shaharil_at_scan-associates.net>

Special thanks: Skywizard <skywizard_at_mybsd.org.my>

Description

Cpanel is web hosting control panel which allow client manage their web account through
web interface. Most of the application are written in perl and compiled to binary.

Details

There is multiple vurnerabilities in this package as describe below.

1) Remote command Execution in guestbook.cgi (/usr/local/cpanel/cgi-sys/guestbook.cgi)

There is classic perl open function vulnerability in template variable which allow any
user to read any file or run command as valid system user which assign to specific url
in apache configuration.

proof of concept:
http://[your site.com]/cgi-sys/guestbook.cgi?user=cpanel&template=|[command]|

2) Local privileges escalation (root)

Cpanel come with openwebmail packages as one of web base email reader which suid root.
In the system with suid perl install perfectly (with suid mode turn on) local user may
include their own perl script when running openwebmail script (oom) through suidperl.

Openwebmail will append perl include path (@INC) through SCRIPT_FILENAME environment variable,
then include some file when execute.

/usr/local/cpanel/base/openwebmail/oom line 14

if ( $ENV{'SCRIPT_FILENAME'} =~ m!^(.?)/[\w\d\-]+\.pl! || $0 =~ m!^(.?)/[\w\d\-]+\.pl! ) { $SCRIPT_DIR=$1;
if (!$SCRIPT_DIR) { print "Content-type: text/html\n\n\$SCRIPT_DIR not set in CGI script!\n"; exit 0; }
push (@INC, $SCRIPT_DIR, ".");
.
.
.
require "openwebmail-shared.pl";

proof of concept:
i) Create file openwebmail-shared.pl contain perl script you want to execute.
ii) Set SCRIPT_FILENAME point to full path of openwebmail-shared.pl file you just create.
iii) exec oom script (ex: suidperl -T /usr/local/cpanel/base/openwebmail/oom )

Vendor status

14th February 2003 - Vendor informed but we received no reply
16th February 2003 - While checking Changelog of the Cpanel, there is a security bug fix in guestbook.cgi
for
Cpanel 6. We believe this is the fix for above bug.

Quick Solution

i) Remove /usr/local/cpanel/cgi-sys/guestbook.cgi.
ii) Turn off suid mode in oom script (chmod 755 /usr/local/cpanel/base/openwebmail/oom).