TFTPD32 Long FileName Remote Denial of Service

2009.11.24
Credit: Sowhat
Risk: Medium
Local: No
Remote: Yes


CVSS Base Score: 5/10
Impact Subscore: 2.9/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: None
Integrity impact: None
Availability impact: Partial

TFTPD32 Long FileName Remote Denial of Service By Sowhat 12.JAN.2005 http://secway.org/advisory/ad20050112.txt Product Affected: tftpd 2.74 and prior Impact: Low OSVDB ID: 12898 (1) Introduction Tftpd32 is a bundle including a full featured TFTP server, a TFTP client, a DHCP server and a Syslog server. Tftpd32 is designed for Windows 95/NT/2000/XP. "Tftpd32 recommended by Cisco, HP and other companies" --From the author's webpage. For more information: http://perso.wanadoo.fr/philippe.jounin/tftpd32.html (2) Details A vulnerability in tftpd32 may allow remote attackers crash the tftpd32 and therefore cause a Denial of Service. aviram(@)beyondsecurity.com had reported "TFTPD32 Buffer Overflow Vulnerability (Long filename)" to bugtraq. And it seems that the author fixed the problem in v2.51. But during the audit, I found that tftpd32 is still vulnerable to "Long Filenmae" issues. C:\Windows\System32>tftp -i 192.168.0.1 get AAAAA...[about 508 'A' here]...AA The tftpd32 will print the following error messages 2 times: "Error:RecvFrom Returns 10040 <"A message sent on a datagram socket was larger than the internal message buffer or some other network limit, or the buffer used to receive a datagram into was smaller than the datagram itself.">" Then, it will dead. But this vulnerability seems very unstable and it's non-exploitable. the tftpd32 will not dead immediately, usually 10-15 seconds after the request, and some times you need to "get" 2-3 times. (3) Solution Waitting for the author's update (4) Author Response I have sent an email to the author BUT no reply yet. Update: 14.Jan.2005 The author replied that the problem will be fixed in next release.

References:

http://www.kb.cert.org/vuls/id/632633
http://www.osvdb.org/12898
http://secway.org/advisory/ad20050108.txt
http://securitytracker.com/id?1012856
http://archives.neohapsis.com/archives/fulldisclosure/2005-01/0386.html


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