Check Point Advisories

Squid Proxy String Processing NULL Pointer Dereference

Vulnerability
Protection

Check Point Reference:	CPAI-2010-380
Date Published:	14 Sep 2010
Severity:	High
Last Updated:	Tuesday 14 September, 2010
Source:
Protection Provided by:	Security Gateway R81, R80, R77, R75
Who is Vulnerable?
Vulnerability Description	The Squid proxy server is a popular open source, Internet proxy and web caching application. It supports various network protocols such as HTTP, FTP, SSL, DNS, and HTCP. It is primarily designed to run on Unix-like systems. A Denial of Service vulnerability exists in Squid Proxy Cache component. The vulnerability is due to an input validation error while parsing crafted strings sent in a request. The vulnerable code does not validate if a string could be NULL before performing a comparison operation. As a result of this, a NULL pointer dereference occurs that leads to a denial of service condition.

Protection Overview

This protection will detect and block attempts to exploit this vulnerability.Note that in order for this defense to protect your Squid Proxy Server, you will need to configure your proxy port to work with the HTTP protocol. For example, if the proxy port is 8080, do the following:1. In the Services tree, click on TCP > HTTP_and_HTTPS_proxy. The TCP Service Properties window opens.2. Click on Advanced. Select the Protocol Type: HTTP.If the proxy works on a different port, you can create a new service with the HTTP protocol type under Services > TCP.

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 Squid Proxy String Processing NULL Pointer Dereference 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: Proxy Server Enforcement Violation.
Attack Information: Squid Proxy string processing null pointer dereference