Unchecked Buffer in Gopher Protocol Handler New

A security vulnerability exists in the Gopher protocol handler of Internet Explorer, Proxy Server and ISA Server which could allow an attacker to exploit a buffer overrun and run code of their choice on the system.

Issue

The Gopher protocol is a legacy protocol that provides for the transfer of text-based information across the Internet. Information on Gopher servers is hierarchically presented using a menu system, and multiple Gopher servers can be linked together to form a collective "Gopherspace".

There is an unchecked buffer in a piece of code which handles the response from Gopher servers. This code is used independently in IE, ISA, and Proxy Server. A security vulnerability results because it is possible for an attacker to attempt to exploit this flaw by mounting a buffer overrun attack through a specially crafted server response. The attacker could seek to exploit the vulnerability by crafting a web page that contacted a server under the attacker's control. The attacker could then either post this page on a web site or send it as an HTML email. When the page was displayed and the server's response received and processed, the attack would be carried out.

A successful attack requires that the attacker be able to send information to the intended target using the Gopher protocol. Anything which inhibited Gopher connectivity could protect against attempts to exploit this vulnerability. In the case of IE, the code would be run in the user's context. As a result, any limitations on the user would apply to the attacker's code as well.

Affected Products

• Microsoft Internet Explorer
• Microsoft Proxy Server 2.0
• Microsoft ISA Server 2000

Solution

Customers can protect themselves against this vulnerability in IE by defining a non-functional Gopher proxy in Internet Explorer. This has the result of essentially disabling the Gopher protocol in IE by making it impossible for IE to send and receive Gopher traffic.

Further Details

Source: Microsoft Corporation

Reference: Microsoft Corporation

Updated: June 11, 2002

>> Recommended Download - secure your PC from spyware, adware and malware now with Spyware Doctor <<