This is Cisco PSIRT's response to the statements made by George Gal
in his advisory: WebSense Content Filter Bypass in conjunction with
Cisco PIX in packet filter mode, posted on May 08, 2006.
The original email/advisory is available at
This issue is being tracked by Cisco Bug IDs:
* CSCsc67612 ( registered customers only) -- Fragmented HTTP
Request Websense URL Filtering Bypass Pix 6.3.x
This Bug ID tracks the issue for PIX software version 6.3 and
older. This DDTS is resolved and available in PIX software version
6.3.5(112). Now workarounds exist to eliminate this issue.
* CSCsc68472 ( registered customers only) -- Fragmented HTTP
Request Websense URL Filtering Bypass PIX/ASA 7.x
This Bug ID tracks the issue for PIX/ASA software version 7.x.
This DDTS is resolved and available in PIX/ASA software versions
7.0(5) and 7.1(2). No workarounds exist to eliminate this issue.
* CSCsd81734 ( registered customers only) -- Segmented HTTP request
bypasses Websense/N2H2 URL filtering
This Bug ID tracks the issue for FWSM software version 2.3 and
3.1. This DDTS is resolved and available in FWSM software versions
2.3(4) and 3.1(1.7). No workarounds exist to eliminate this issue.
Our May 8, 2006 reply is available at:
We would like to thank George Gal of Virtual Security Research for
reporting this issue to us.
We greatly appreciate the opportunity to work with researchers on
security vulnerabilities, and welcome the opportunity to review and
assist in product reports.
If various PIX/ASA/FWSM software versions are configured to use
Websense/N2H2 for content filtering, users may be able to bypass HTTP
content restrictions. By fragmenting the GET method of an HTTP
request into multiple packets, it is possible to cause a condition in
which the PIX/ASA/FWSM firewall will mistakenly allow a restricted
website to be accessed. The PIX/ASA/FWSM firewall expects the entire
GET method to be received in one packet. There are no workarounds
which mitigate or eliminate this issue.
PIX software version 6.3.5(112) and later resolves this issue.
Interim releases of PIX 6.3 software are only available by contacting
the Cisco TAC or your Cisco support partner. Please reference this
security response when requesting software to ensure the proper
software version is obtained.
PIX/ASA software versions 7.0(5) and 7.1(2) resolve this issue.
Maintenance releases of PIX/ASA 7.x software may be downloaded at the
FWSM software versions 2.3(4), 3.1(1.7) and later resolve this issue.
FWSM software version 2.3(4) may be downloaded at the following site.
Interim releases of FWSM 3.1 software are only available by
contacting the Cisco TAC or your Cisco support partner. Please
reference this security response when requesting software to ensure
the proper software version is obtained.
Cisco Security Procedures
Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and
registering to receive security information from Cisco, is available
on Cisco's worldwide website at http://www.cisco.com/warp/public/707/
sec_incident_response.shtml. This includes instructions for press
inquiries regarding Cisco security notices. All Cisco security
advisories are available at http://www.cisco.com/go/psirt.