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@stake, Inc.
www.atstake.com
Security Advisory
Advisory Name: Norton Personal Internet Firewall HTTP Proxy Vulnerability
Release Date: 07/15/2002
Application: AtGuard v3.2
Norton Personal Internet Firewall 2001 v3.0.4.91
Platform: Microsoft Windows NT4 SP6a
Microsoft Windows 2000 SP2
Severity: A buffer overflow occurs potentially allowing the
execution of arbitrary code
Author: Ollie Whitehouse (ollie@atstake.com)
Vendor Status: Informed and patch available
CVE Candidate: CAN-2002-0663
Reference: www.atstake.com/research/advisories/2002/a071502-1.txt
Overview:
Symantec (http://www.symantec.com/) Norton Personal Internet
Firewall is a widely used desktop firewalling application for
Microsoft Windows NT, 98, ME and 2000 platforms. Typically personal
firewalls are deployed upon mobile workstations that leave the enterprise
and may be deployed upon public networks to enable them to establish
connectivity back to the corporation and thus require protection from
malicious attackers while outside the confines of the enterprise firewall.
There exists a vulnerability within the NPIF's HTTP proxy that allows an
attacker to overwrite the first three (3) bytes of the EDI register and
Thus potentially execute malicious code.
This vulnerability is exploitable even if the requesting application is
not configured in the firewall permission setting to make outgoing
requests. An example of such a scenario would be a malicious web page that
contains a disguised link which contains sufficient data to exploit this
vulnerability.
Details:
There is a vulnerability with the way in which the NT kernel based
HTTP proxy of NPIF deals with a large amount of data, that causes a buffer
overflow to occur. The test scenario that @stake used to cause this
Exception was as follows:
NPIF configured to allow only Microsoft Internet Explorer out on TCP port
80 to the public internet. A large outgoing request is then made by a third
party application (i.e. malicious code). If the exploitation is
unsuccessful a NT kernel exception will be thrown typically overwriting EDI
with user supplied data. If exploitation is successful an attacker can run
arbitrary code within the KERNEL.
Vendor Response:
This issue was reported to Symantec on April 18, 2002. Symantec has an
Update that solves this problem. Symantec's advisory regarding this issue
can be found here (wrapped):
http://securityresponse.symantec.com/avcenter/security/
SymantecAdvisories.html
Recommendations:
Due to the fact that this attack has to occur from the host computer
@stake recommends that there should be a multi-layered approach to
security. This should include anti-virus, user education/awareness as
well as ensuring that vendor patches are deployed for all relevant
software products.
Users should install the update for Norton Personal Internet Firewall 2001.
Common Vulnerabilities and Exposures (CVE) Information:
The Common Vulnerabilities and Exposures (CVE) project has
assigned the following names to these issues. These are candidates for
inclusion in the CVE list (http://cve.mitre.org), which standardizes
names for security problems.
CAN-2002-0663 Norton Personal Internet Firewall Buffer Overflow
@stake Vulnerability Reporting Policy:
http://www.atstake.com/research/policy/
@stake Advisory Archive:
http://www.atstake.com/research/advisories/
PGP Key:
http://www.atstake.com/research/pgp_key.asc
Copyright 2002 @stake, Inc. All rights reserved.
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