Check Point Advisories

OpenSSH sshd Identical Blocks Denial of Service (CVE-2006-4924)

Vulnerability
Protection

Check Point Reference:	CPAI-2006-300
Date Published:	21 Oct 2009
Severity:	High
Last Updated:	Monday 02 April, 2012
Source:
Industry Reference:	CVE-2006-4924
Protection Provided by:	Security Gateway R81, R80, R77, R75
Who is Vulnerable?
Vulnerability Description	The Secure Shell (SSH) protocol is a well-established method of secure communication in a client and server architectural model. The protocol was developed and implemented as an alternative to the older remote connection programs, such as telnet, rsh and rlogin, which offer limited to no security. SSH is based on the idea of a public key exchange, where a server offers a client its public key. The client then uses this key to encrypt all communication between the two machines, including its own encryption key. There exists a denial of service vulnerability in the SSH1 protocol implementation in OpenSSH. The flaw is caused by incorrect processing of duplicated incoming blocks. An unauthenticated attacker may exploit this vulnerability to force the openssh server to consume large amounts of CPU time. Under successful attack, the target OpenSSH server may utilize a large amount of CPU resources for a limited amount of time, causing system performance degradation and possibly resulting in a denial of service condition of the SSH service.

Protection Overview

This protection will detect and block attempts to exploit this vulnerability

In order for the protection to be activated, update your Security Gateway product to the latest IPS update. For information on how to update IPS, go to SBP-2006-05, click on Protection tab and select the version of your choice.

Security Gateway R80 / R77 / R75

In the IPS tab, click Protections and find the OpenSSH sshd Identical Blocks Denial of Service protection using the Search tool and Edit the protection's settings.
Install policy on all Security Gateways.

This protection's log will contain the following information:

Attack Name: SSH Protection Violation.
Attack Information: OpenSSH sshd identical blocks denial of service