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Vulnerability Alert

Cisco ASA Adaptive Security Appliance Software Clientless SSL VPN Rot13-Encoded Cross-Site Scripting Vulnerability

 
Threat Type:
IntelliShield ID:18442
Version:2
First Published:2009 June 24 16:11 GMT
Last Published:2009 July 22 16:26 GMT
Port: Not available
CVE:CVE-2009-1202
Urgency:Unlikely Use
Credibility:Confirmed
Severity:Harassment
CVSS Base:4.3 CVSS Calculator
CVSS Version 2.0
CVSS Temporal:3.6
 
Version Summary:

This alert has been updated to clarify that versions 7.x of the Cisco ASA Software are not affected by the Cisco ASA Adaptive Security Appliance Software clientless SSL VPN Rot13-encoded cross-site scripting vulnerability.

 
 
Description

Cisco ASA Adaptive Security Appliance Software versions prior to 8.0.4(34), 8.1.2(25), and 8.2.1(3) that have been configured to accept Clientless SSL VPN connections contain a cross-site scripting vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary script or HTML code in a user's browser session.  Versions 7.x are not affected.

The vulnerability is due to insufficient restrictions on Rot13-encoded URL parameters that are utilized by the SSL VPN feature of Cisco ASA Software when clients browse web pages by means of the VPN web portal.  An attacker who could convince a user to visit a malicious page while logged into the secure portal could exploit this vulnerability to execute arbitrary script or HTML code in the security context of the affected site.

Cisco has confirmed this vulnerability and released updated software.

 
Warning Indicators

Cisco ASA Software versions prior to 8.0.4(34), 8.1.2(25), and 8.2.1(3) are affected when they are running on 5505, 5510, 5520, 5540, 5550, and 5580 devices.

Cisco ASA Software versions 7.x are not affected.

 
IntelliShield Analysis

The vulnerability is due to a failure to properly protect the domain object model that is utilized by the Clientless SSL VPN against unauthorized modification.? The vulnerability is likely to be exploited in instances where administrators allow users to enter arbitrary URLs that could be visited by means of the secure web portal.? Systems that allow users to visit only the URLs that have been defined by administrators are less likely to be affected.? In the latter case, an attacker would need to take control of a website that resides at one of the predefined URLs or perform URL spoofing or hijacking to conduct an attack.

Exploit code that demonstrates the cross-site scripting vulnerability is publicly available.

 
Vendor Announcements

Cisco has released a Release Note Enclosure for Cisco bug ID CSCsy80705.

This vulnerability was reported to Cisco by Charles Henderson and David Byrne of Trustwave's SpiderLabs.

 
Impact

An unauthenticated, remote attacker could exploit this vulnerability to run arbitrary script or HTML code in the security context of the affected site.? An exploit could allow the attacker to access sensitive browser based information such as authentication cookies or recently submitted data.? An exploit could also allow an attacker to modify the appearance of the affected site.

 
Technical Information

The vulnerability is due to improper use of Rot13-encoded URL components that are utilized by the SSL VPN functionality of Cisco ASA Software.? This processing of malicious URLs could allow for the execution of arbitrary script or HTML code.

An unauthenticated, remote attacker could exploit this vulnerability by convincing a user to view a malicious web page within the SSL VPN portal.? A successful attack could allow the execution of arbitrary script or HTML code as well as modify the appearance of the affected web page.

 
Safeguards

Administrators are advised to apply the appropriate updates.

Administrators are advised to allow only trusted users to have network access.

Administrators are advised to configure the Clientless SSL VPN web portal to restrict users to administratively defined websites.

Administrators are advised to configure Web Access Control Lists (ACLs) to restrict users to internal or authorized resources.

Users are advised not to follow unsolicited links.? Users should verify the authenticity of unexpected links prior to following them.

Users are advised not to visit websites or follow links that have suspicious characteristics or cannot be verified as safe.

 
Patches/Software

Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at tac@cisco.com.

A special download page on the Software Center?is available that contains fixed software releases at the following link: ASA-PSIRT


Signatures
 
Cisco Intrusion Prevention System (IPS) 6.0
Signature IDSignature NameReleaseLatest Release Date
18799/0Cisco ASA WebVPN Cross Site ScriptingS4492009 Nov 19 
 
Alert History
 

Version 1, June 24, 2009, 12:11 PM:  Cisco ASA Adaptive Security Appliance Software contains a cross-site scripting vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary script or HTML code in a user's browser.  Updates are available.



Product Sets
 
The security vulnerability applies to the following combinations of products.

Primary Products:
CiscoCisco Adaptive Security Appliance (ASA) Software 8.0 .1.2, .2, .2.11, .3, .4, .4.25, .4.28, .4.32, .4.33 | 8.1 Base, .1, .2, .2.15, .2.16, .2.19, .2.23, .2.24 | 8.2 .0.45

Associated Products:
N/A




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LEGAL DISCLAIMER
The urgency and severity ratings of this alert are not tailored to individual users; users may value alerts differently based upon their network configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.
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