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  Многочисленные уязвимости безопасности в Plex Media Server

From:SEC Consult Vulnerability Lab <research_(at)_sec-consult.com>
Date:5 мая 2014 г.
Subject:SEC Consult SA-20140411-0 :: Multiple vulnerabilities in Plex Media Server

SEC Consult Vulnerability Lab Security Advisory < 20140411-0 >
             title: Multiple vulnerabilities
           product: Plex Media Server
vulnerable version: confirmed in
     fixed version: none
            impact: High
          homepage: http://www.plex.tv
             found: 2014-02-06
                by: Stefan Viehbock
                    SEC Consult Vulnerability Lab

Vendor/product description:
"Plex is a media player system consisting of a player application with a
10-foot user interface and an associated media server. It is available for
Mac OS X, Linux, and Microsoft Windows."

URL: https://en.wikipedia.org/wiki/Plex_(software)

Vulnerability overview/description:
1. Use of plain text protocols
Plain text protocols are used in various places.

The Plex App Store fetches App listings and App code via HTTP. This enables
active attackers (MITM) to run code in the context of the Plex Media Server.
The Plex "Remote" functionality uses HTTP as well. This enables passive
attackers to gain access to the session token in order to access the Plex Media
Server web interface.

2. Insecure use of SSL/TLS
The Plex Media Server offers HTTPS access via TCP port 32443. The certificate
that is used is issued by "DigiCert Secure Server CA" which is a commonly
trusted certificate authority. The certificate is issued to "*.hub.plex.tv".
The private key for this certificate is included in the Plex software and can
be extracted easily.
The DNS server behind "hub.plex.tv" is configured to resolve subdomains
relative to the IP indicated in the name. Eg. 1-2-3-4.hub.plex.tv resolves
to the IP This enables all Plex Media Servers to offer SSL/TLS
services out of the box without prior configuration and using a valid
For this to work the corresponding private key has to be included in the
software. This enables active attackers to execute SSL MITM attacks as the
private key is effectively public.

This mechanism can be abused by malicious entities to provide services on
arbitrary IPs via SSL/TLS as well. One example would be to run a
watering-hole-style attack by abusing the reputation of the Plex domain as
well as the valid certificate.

As this mechanism requires the private key to be compromised it should not be
used in the first place. The certificate should be revoked.

The Plex Media Server seems to offer DHE ciphers (DHE_RSA). The perfect forward
secrecy (PFS) properties of these KEX ciphers would prevent passive attackers
from decrypting communication.

3. Unauthenticated information disclosure through stack traces
Python stack traces are included in the responses for some requests. This
allows an attacker to gain information about the target operating system,
local file paths etc. which can be used in further attacks.

4. Cross Site Request Forgery
The application does not implement any kind of CSRF protection. Quite the
contrary, security mechanisms that would minimize the extent of CSRF attacks
are deliberately disabled. The Plex Media Server explicitly allows all
sources (wildcard) in cross-server resource sharing (CORS) as well as in
cross-domain policy restrictions (Flash and Silverlight). This enables
attackers to retrieve arbitrary content (eg. the master token) from the

Proof of concept:
1. Use of plain text protocols
No proof of concept needed.
The Plex App store is located at: http://nine.plugins.plexapp.com

2. Insecure use of SSL/TLS
The private key for the "*.hub.plex.tv" certificate:


3. Unauthenticated information disclosure through stack traces
The following request causes an exception in the application logic.

GET /system/proxy HTTP/1.1
Host: <HOST>
X-Plex-Url: http://my.plexapp.com/NONEXISTANT

A stack trace is included in the server's response:

HTTP/1.0 500 Internal Server Error
Content-Length: 3437
Content-Type: application/xml
Cache-Control: no-cache
X-Plex-Protocol: 1.0

<?xml version='1.0' encoding='utf-8'?>
<Response code="2000" status="HTTPError: ">
 <Traceback>Traceback (most recent call last):
 File "C:\Users\user\AppData\Local\Plex Media
line 845, in handle_request
   result = f(**d)
 File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 629, in
   return self.parent.open(new, timeout=req.timeout)
 File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 410, in open
   response = meth(req, response)
 File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 523, in
   'http', request, response, code, msg, hdrs)
 File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 448, in error
   return self._call_chain(*args)
 File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 382, in _call_chain
   result = func(*args)
 File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 531, in
   raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
HTTPError: HTTP Error 404: Not Found

4. Cross Site Request Forgery
No CSRF tokens are implemented.
The files crossdomain.xml and clientaccesspolicy.xml in the webroot allow
both Silverlight and Flash to send arbitrary requests to the server and
receive responses.
Some pages respond with the "Access-Control-Allow-Origin: *" headers.

Vulnerable / tested versions:
The vulnerabilities have been verified to exist in Plex Media Server version

Vendor contact timeline:
2014-02-09: Contacting vendor through [email protected] and requesting
           encryption keys.
2014-02-10: Vendor provides encryption keys.
2014-02-10: Sending advisory and proof of concept exploit.
2014-02-10: Vendor acknowledges receipt of advisory.
2014-02-17: Requesting status update.
2014-02-21: Requesting clarification regarding fixed version.
2014-02-21: Vendors provides further information about reported vulnerabilities.
2014-02-24: Requesting clarification regarding patching status and setting
deadline (2014-03-24).
2014-02-25: Vendor announces that the certificate will be revoked soon.
2014-04-04: Requesting status update.
2014-04-05: Vendor confirms that certificate has been revoked. No other fixes
have been implemented.
2014-04-11: SEC Consult releases security advisory.

No solution is available.

No workaround available.

Advisory URL:

SEC Consult Vulnerability Lab

SEC Consult
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Mooslackengasse 17, 1190 Vienna, Austria
Phone:   +43 1 8903043 0
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Interested in working with the experts of SEC Consult?
Write to [email protected]

EOF Stefan Viehbock / @2014

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