[EXPL] SunFTP vulnerable to two Denial-of-Service attacks (long buffer, half-open)

2000-09-02T00:00:00
ID SECURITYVULNS:DOC:626
Type securityvulns
Reporter Securityvulns
Modified 2000-09-02T00:00:00

Description

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com

SunFTP vulnerable to two Denial-of-Service attacks (long buffer, half-open)

SUMMARY

<http://xs4all.dk/sunftp/> SunFTP is a small FTP server written in Delphi. This product contains a few vulnerabilities in its socket module. First, it is possible to cause it to overflow its receiving buffer. Second, SunFTP can be crashed remotely by disconnecting the session without sending a complete command.

DETAILS

Vulnerable systems: SunFTP Build: 9(1)

Buffer overflow problem: To test for this vulnerability, connect to the server and send a buffer of 2100 characters.

(Cmd: perl -e "print \"GET @{['x'x2100]} HTTP/1.0\n\n\""|nc 127.1 80

The server crashes, and this enables attackers to launch a Denial of Service attack against the product.

Half-open DoS: To test for this vulnerability, connect to the server with a non-FTP program (for example, telnet). Now disconnected immediately (or after sending a buffer), but make sure you don't send a newline ('\r\n'). The server will crash almost immediately.

Workaround / Solution: Since this is a discontinued project, and the author has not responded to our email, we suggest switching to another FTP Server.

Detection: It is possible to detect a vulnerable SunFTP server by looking for the following FTP banner: 220 hostname FTP Server (SunFTP b9) ready on port 21.

ADDITIONAL INFORMATION

The security hole was discovered by Beyond Security's SecuriTeam (expert@securiteam.com).

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-- Aviram Jenik Beyond Security Ltd. http://www.BeyondSecurity.com http://www.SecuriTeam.com