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Potential DOS Vulnerability in WFTPD
WFTPD v3.00R5 is an ftp server available from http://www.wftpd.com and http://www.download.com. A potential denial-of-service vulnerability exists which allows a remote attacker to hang the server.
When a user attempts to change the current directory, the server first queries the directory, then determines if the operation should be allowed. This implementation exposes the server to a DOS attack if a malicious attacker continuously tries to change the current directory to the server's floppy drive. The following is an illustration of the problem:
> ftp localhost Connected to xxxxxxxxxx.rh.rit.edu. 220-This FTP site is running a copy of WFTPD that is NOT REGISTERED .. .. <registration nag header is edited out > .. 220 WFTPD 3.0 service (by Texas Imperial Software) ready for new user User (xxxxxxxxxx.rh.rit.edu:(none)): jdog 331 Give me your password, please Password: 230 Logged in successfully ftp> cd a:/ 501 User is not allowed to change to a:/ - returning to /. ftp>
The server correctly denies the action, but queries the A:\ drive
anyway. A DOS can achieved by repeating the 'cd a:/' command continuously. This problem will have varying effects, depending on your system configuration. An exploit written in PERL is available at: http://hogs.rit.edu/~joet/code/floppy_hell.pl
Disable your floppy drive in your system BIOS if your system configuration is vulnerable.
Texas Imperial Software was contacted via <email@example.com> and <firstname.lastname@example.org> on Wednesday, April 25, 2001. Alun Jones, the program author, verified the behavior and plans on releasing a fix in the v3.1 branch.
- Joe Testa
e-mail: email@example.com web page: http://hogs.rit.edu/~joet AIM: LordSpankatron
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