Paessler PRTG Network Monitor 14.4.12.3282 XXE Injection

`Advisory: XML External Entity Expansion in Paessler PRTG Network Monitor  
  
Authenticated users who can create new HTTP XML/REST Value sensors in  
PRTG Network Monitor can read local files on the PRTG host system via  
XML external entity expansion.  
  
  
Details  
=======  
  
Product: Paessler PRTG Network Monitor  
Affected Versions: 14.4.12.3282  
Fixed Versions: 16.2.23.3077/3078  
Vulnerability Type: XML External Entity Expansion  
Security Risk: medium  
Vendor URL: https://www.paessler.com/  
Vendor Status: fixed version released  
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2015-012  
Advisory Status: published  
CVE: CVE-2015-7743  
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-7743  
  
  
Introduction  
============  
  
"PRTG Network Monitor is the powerful and comprehensive network  
monitoring solution from Paessler AG. It monitors your network using a  
whole range of technologies and assures the availability of network  
components and measures traffic and usage. PRTG saves costs by avoiding  
outages, optimizing connections, saving time and controlling service  
level agreements (SLAs)."  
  
(from the vendor's website)[1]  
  
  
More Details  
============  
  
An attacker with access to a PRTG Network Monitor account with  
sufficient privileges to create or configure XML/REST sensors can read  
files stored on the system's local disk. These sensors are intended to  
query a URL and, depending on the configuration, check whether there is  
a valid response or read the value of a specific XML node in the  
document that is returned. This functionality is vulnerable to XML  
external entity expansion.  
  
  
Proof of Concept  
================  
  
In order to exploit this vulnerability an HTTP XML/REST Value sensor has  
to be set up to access an attacker-controlled URL and to read the value  
of a specific XML node, for example:  
  
https://attacker.example.com/xeee-hosts.xml  
  
The XML document "xeee-hosts.xml" contains an external entity that uses  
the "SYSTEM" keyword to load a local file as the content of the "hosts"  
entity:  
  
<?xml version="1.0"?>  
<!DOCTYPE root [  
<!ENTITY hosts SYSTEM "file://C:\Windows\System32\drivers\etc\hosts">  
]>  
<root>&hosts;</root>  
  
Since the XML parser of PRTG Network Monitor evaluates external  
entities, the XML parser fetches the file  
  
"C:\Windows\System32\drivers\etc\hosts"  
  
from the disk of the local system and inserts its content into the  
"root" node of the XML document. If the sensor is configured to return  
the value of that "root" node, the contents of that file are displayed  
in the web interface of PRTG Network Monitor. This discloses the  
contents of the file to attackers which otherwise would not be able to  
read local files.  
  
  
Fix  
===  
  
Update to a version greater or equal to 16.2.23.3077/3078 (see [2]).  
  
  
Security Risk  
=============  
  
Attackers who can create new HTTP XML/REST sensors in PRTG Network  
Monitor, are able to use the XML external entity expansion to read files  
on the local system. Depending on the data stored on the vulnerable  
system, this vulnerability may pose a high risk. However, as attackers  
are required to already have valid user credentials for the application,  
the vulnerability is only rated to have a medium risk potential.  
  
  
Timeline  
========  
  
2015-08-28 Vulnerability identified in PRTG Network Monitor  
2015-09-04 Customer approved disclosure of vulnerability  
2015-09-04 CVE ID requested  
2015-09-24 CVE ID requested again  
2015-10-07 CVE ID assigned  
2015-10-21 Vendor contacted  
2016-04-04 Vendor released fixed version  
2016-05-31 Advisory released  
  
  
References  
==========  
  
[1] https://www.paessler.com  
[2] https://www.paessler.com/prtg/history/stable  
  
  
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  
https://www.redteam-pentesting.de.  
  
  
--   
RedTeam Pentesting GmbH Tel.: +49 241 510081-0  
Dennewartstr. 25-27 Fax : +49 241 510081-99  
52068 Aachen https://www.redteam-pentesting.de  
Germany Registergericht: Aachen HRB 14004  
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`