Advisory

Han Sahin, September 2015

Multiple Cross-Site Scripting vulnerabilities in Synology Download Station

Abstract

Multiple Cross-Site Scripting vulnerabilities were found in Synology Download Station. These issues allow attackers to perform a wide variety of actions, such as stealing victims' session tokens or login credentials if available, performing arbitrary actions on their behalf but also performing arbitrary redirects to potential malicious websites.

Tested version

These issues have been tested on Synology Download Station version 3.5-2956 and version 3.5-2962.

Fix

Synology reports that these issue have been resolved in:

- Download Station version 3.5-2962 [Create download task via file upload]
- Download Station version 3.5-2967 [Create download task via URL]

Introduction

/advisory/SFY20150809/synology_diskstation_ds214play.png
Download Station is a popular Synology web application with more than 6.879.000 installations. Synology Download Station users can download files from multiple file hosting sites like BT, FTP, HTTP, NZB, Thunder, eMule, and more. Download Station is generally used by users that use their NAS as an entertainment hub, residing within the user's home network. Most users do not realize that these NAS devices are an entry point for attackers into their home network.

Multiple Cross-Site Scripting vulnerabilities were found in Synology Download Station. These issues allow attackers to perform a wide variety of actions, such as stealing victims' session tokens or login credentials if available, performing arbitrary actions on their behalf but also performing arbitrary redirects to potential malicious websites.

Persistent Cross-Site Scripting in "Create download task via file upload"

Users can create download tasks by uploading files (.torrent, .NZB or .txt) to Download Station. The "Create download task via file upload" feature is vulnerable to persistent Cross-Site Scripting. An attacker can create a specially crafted Torrent file containing a Cross-Site Scripting payload via the 'name' parameter. If a victim uses the "Create download task via file upload" feature to import file in Download Station, the payload will be executed within the browser context of the (authenticated) victim.

This Torrent file demonstrates this vulnerability in Download Station. The following video shows how a Torrent file can be used to load an arbitrary website in an iframe.

Persistent Cross-Site Scripting vulnerability in Synology Download Station from Securify BV on Vimeo.

Persistent Cross-Site Scripting in "Create download task via URL"

Users can create download tasks by manually entering URLs or searching for Torrent files with BT Search. The "Create download task via URL" feature is vulnerable to persistent Cross-Site Scripting. An victim can unknowingly download a malicious Torrent file through BT Search containing an Cross-Site Scripting payload in the download site URL.

/advisory/SFY20150809/urls_synology_xss.png

Proof of concept

GET /webman/3rdparty/DownloadStation/dlm/downloadman.cgi?urls=%5B%22http%3A%2F%2Fwww.securify.nl%2Fsec%3Ciframe%20src%3D'http%3A%2F%2Fwww.hackaday.com'%2F%3E.torrent%22%5D&action=add_url_task&desttext=video&file_info=on HTTP/1.1
Host: 192.168.1.14:5000
User-Agent: Mozilla/5.0
X-SYNO-TOKEN: l1ekJnPhUXm5o
Cookie: stay_login=0; id=l1GnmfyQR60ms13A0LTN001710
Connection: keep-alive
Pragma: no-cache
Cache-Control: no-cache

It should be noted that the X-SYNO-TOKEN header provides protection against Cross-Site Request Forgery attacks. As of DSM version 5.2-5592 Update 3, this protection is enabled by default. In addition the DS Video app requests do not include this Cross-Site Request Forgery protection.

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