Title: HTC / Windows Mobile OBEX FTP Service Directory Traversal
Author: Alberto Moreno Tablado
Vendor:
HTCVulnerable Products:
- HTC devices running Windows Mobile 6
- HTC devices running Windows Mobile 6.1
Non vulnerable products:
- HTC devices running Windows Mobile 5.0
- HTC devices running Windows Mobile 6.5
- Other vendors' Windows Mobile devices
DescriptionHTC devices running Windows Mobile 6 and Windows Mobile 6.1 are prone to a directory traversal vulnerability in the Bluetooth OBEX FTP Service. The service is located in a 3rd party driver developed by HTC and installed on HTC devices running Windows Mobile, so the vulnerability only affects to this vendor specifically.
The scope of the Directory Traversal vulnerability allows a remote attacker to traverse to parent directories out of the default Bluetooth shared folder by using ../ or ..\\ marks. This security flaw leads to browse folders located anywhere in the file system, download files contained in any folder as well as upload files to any folder, which may lead to code execution.
A remote attacker who previously owned authentication and authorization rights over Bluetooth can perform three risky actions on the device:
1) Browse directories located out of the limits of the default shared folder
The attacker can discover the structure of the file system and access to any directory within it, including:
- The flash hard drive
- The external storage card
- The internal mass storage memory, included in specific HTC devices
2) Download files without permission
The attacker can download sensitive files located anywhere in the file system, such as:
- personal pictures and documents located in \My Documents or any other directory
- Contacts, Calendar & Tasks information located in \PIM.vol
- Temporary internet cache and cookies located in \Windows\Profiles\guest
- emails located in \Windows\Messaging
3) Upload malicious files
The attacker can replace third party or system executable files with malicious files as well as upload trojans to any place in the filesystem, such as \Windows\Startup and, therefore, shall be executed the next time Windows Mobile inits.
The following HTC devices are affected by this vulnerability:
- HTC devices running Windows Mobile 6 Professional
- HTC devices running Windows Mobile 6 Standard
- HTC devices running Windows Mobile 6.1 Professional
- HTC devices running Windows Mobile 6.1 Standard
Here you can find a list of tested HTC devices proved to be vulnerable.
HTC devices running Windows Mobile 5.0 are not affected because the OBEX FTP service is not implemented in that OS version.
Other vendors' Windows Mobile devices are not affected either: ASUS, Samsung, LG, ...
Vendor StatusThe vulnerability was first disclosed on 2009/01/19 as a whole Microsoft Bluetooth Stack issue in Windows Mobile 6 Professional. Subsequent tests proved that several Windows Mobile 6 Standard and Windows Mobile 6.1 Professional devices were also vulnerable. Microsoft was contacted on 2009/01/22 and this information was not made public because last mobile phones manufactured were vulnerable.
Further investigations proved that the issue is in a 3rd party driver installed by HTC, this vulnerability only affects to HTC devices and other vendors' Windows Mobile devices are not affected.
HTC Europe was contacted several times since 2009/02 until 2009/06. Through out this period of time I attempted to collaborate with the vendor and provided all the details concerning on the exploitation of the flaw. However, I failed to coordinate the disclosure of the advisory and the release of the hotfix so finally I was forced to go public with all the information undisclosed.
Having the vulnerability been announced HTC commenced to release hotfixes.
This vulnerability is a zero-day threat. This means that all devices shipped up to date (July 2009) may be vulnerable.
Read the full advisory here.
