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Vulnerability Alert

Cisco ASA VPN Denial of Service Vulnerability

 
Threat Type:CWE-399: Resource Management Errors
IntelliShield ID:31397
Version:1
First Published:2013 October 22 15:18 GMT
Last Published:2013 October 22 15:18 GMT
Port: Not available
CVE:CVE-2013-5544
BugTraq ID:63262
Urgency:Unlikely Use
Credibility:Confirmed
Severity:Mild Damage
CVSS Base:5.4 CVSS Calculator
CVSS Version 2.0
CVSS Temporal:4.5
 
Version Summary:Cisco Adaptive Security Appliance Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
 
 
Description
A vulnerability in the VPN authentication code that handles parsing of the username from the certificate on the Cisco ASA firewall could allow an unauthenticated, remote attacker to cause a reload of the affected device.

The vulnerability is due to parallel processing of a large number of Internet Key Exchange (IKE) requests for which username-from-cert is configured. An attacker could exploit this vulnerability by sending a large number of IKE requests when the affected device is configured with the username-from-cert command. An exploit could allow the attacker to cause a reload of the affected device, leading to a denial of service (DoS) condition.

Cisco has confirmed the vulnerability in a security notice and released software updates.
 
Warning Indicators
At the time this alert was first published, Cisco ASA Software versions 8.4(4.5) and prior were vulnerable. Later releases of Cisco ASA may also be vulnerable.
 
IntelliShield Analysis
To exploit this vulnerability, an attacker must send a large number of IKE requests to a targeted device, which may reside on trusted, internal networks that the attacker would likely need to access. This access requirement decreases the likelihood of a successful exploit. In addition, the targeted device must be configured with the username-from-cert command.

Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
 
Vendor Announcements
Cisco has released a security notice at the following link: CVE-2013-5544

Customers are advised to consult Cisco bug ID CSCua91108 for a complete list of affected product versions.
 
Impact
An unauthenticated, remote attacker could exploit this vulnerability to cause an affected device to reload, resulting in a DoS condition.
 
Technical Information
The vulnerability is due to parallel processing of a large number of IKE requests for which username-from-cert is configured.

An unauthenticated, remote attacker could exploit this vulnerability by sending a large number of IKE requests when the affected device is configured with the username-from-cert command. An exploit could allow the attacker to cause a reload of the affected device, leading to DoS condition.
 
Safeguards
Administrators are advised to apply the appropriate updates.

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

Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.

Administrators are advised to monitor affected systems.
 
Patches/Software
Cisco customers with active contracts should contact their Cisco support team for assistance in upgrading to a software version that includes fixes for this vulnerability. Cisco customers without contracts may contact the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email at tac@cisco.com for assistance.
 
Alert History
 
Initial Release


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

Primary Products:
CiscoCisco Adaptive Security Appliance (ASA) Software 8.4 .1, .1.3, .1.11, .2, .2.1, .2.8, .3, .3.8, .3.9, .4, .4.1, .4.3, .4.5

Associated Products:
N/A




Alerts and bulletins on the Cisco Security Intelligence Operations Portal are highlighted by analysts in the Cisco Threat Operations Center and represent a subset of the comprehensive content that is available through Cisco Security IntelliShield Alert Manager Service. This customizable threat and vulnerability alert service provides security staff with access to timely, accurate, and credible information about threats and vulnerabilities that may affect their environment.


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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