Vulnerability Note VU#868219

Multiple vendors' HTTP content/virus scanners do not check data tunneled via HTTP CONNECT method

Original Release date: 15 Oct 2002 | Last revised: 15 Oct 2002


Multiple vendors' HTTP anti-virus and content filters do not inspect the contents of HTTP CONNECT method tunnels. As a result, viruses or other restricted HTTP content may not be blocked as specified by policy.


Many anti-virus and content filter products that are designed to inspect HTTP application data rely on HTTP proxy functionality to examine the contents of HTTP connections. In turn, HTTP proxy services commonly support the HTTP CONNECT method, which is designed to create a TCP connection that bypasses the normal application layer functionality of the proxy. Typically, the HTTP CONNECT method is used to tunnel HTTPS connections through an HTTP proxy. The application layer data in an HTTP CONNECT method tunnel is opaque to the proxy service. The default configurations of many HTTP proxy services allow arbitrary TCP connections to be made using the HTTP CONNECT method [VU#150227].

As most HTTP proxy services ignore the HTTP data contained within an HTTP CONNECT method tunnel, so do most HTTP anti-virus and content scanners. As a result, it may be possible to create an HTTP CONNECT method tunnel through a vulnerable HTTP anti-virus or content scanner and transfer viruses or other restricted HTTP content.


A malicious actor may be able to bypass HTTP anti-virus software and HTTP content restrictions by transferring data via an HTTP CONNECT method tunnel.


Upgrade or Patch

Upgrade or apply a patch as specified by your vendor.

Architect HTTP Content Inspection

Depending on the behavior of different HTTP proxy and HTTP anti-virus/content inspection products, it may be possible to design a system that is able to inspect data that has passed through an HTTP CONNECT method tunnel.

Examine Tunneled Data

If possible, configure your HTTP anti-virus/content filters to examine the application layer contents of HTTP CONNECT method tunnels.

Use Desktop Anti-Virus Software

Deploy and maintain updated anti-virus software on client systems.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
Trend MicroAffected-15 Apr 2002
F-SecureNot Affected19 Apr 200205 Jun 2002
F5 NetworksNot Affected19 Apr 200228 May 2002
Hewlett-Packard CompanyNot Affected19 Apr 200229 May 2002
SophosNot Affected19 Apr 200230 May 2002
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



The CERT/CC thanks Peter Bieringer and AERAsec Network Services and Security GmbH for information used in this document.

This document was written by Art Manion.

Other Information

  • CVE IDs: Unknown
  • Date Public: 22 Feb 2002
  • Date First Published: 15 Oct 2002
  • Date Last Updated: 15 Oct 2002
  • Severity Metric: 8.69
  • Document Revision: 18


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