AV:N/AC:M/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:C
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A vulnerability in the Identity Firewall feature of Cisco ASA Software could allow an unauthenticated, remote attacker to cause a reload of the affected system or to remotely execute code.
The vulnerability is due to a buffer overflow in the affected code area. An attacker could exploit this vulnerability by sending a crafted NetBIOS packet in response to a NetBIOS probe sent by the ASA software. An exploit could allow the attacker to execute arbitrary code and obtain full control of the system or cause a reload of the affected system.
Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems configured in routed and transparent firewall mode and in single or multiple context mode. This vulnerability can be triggered by IPv4 traffic.
Cisco has released software updates that address this vulnerability. There is a workaround that addresses this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161019-asa-idfw
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Affected Cisco ASA Software running on the following products may be affected by this vulnerability:
- Cisco ASA 5500 Series Adaptive Security Appliances
- Cisco ASA 5500-X Series Next-Generation Firewalls
- Cisco Catalyst 6500 Series/7600 Series ASA Services Module
- Cisco ASA 1000V Cloud Firewall
- Cisco Adaptive Security Virtual Appliance (ASAv)
- Cisco ASA for Firepower 9300 Series
- Cisco ASA for Firepower 4100 Series
- Cisco ISA 3000 Industrial Security Appliance
Refer to the "Fixed Software" section of this security advisory for more information about the affected releases.Vulnerable Products
This vulnerability affects Cisco ASA Software configured with the Identity Firewall feature and with NetBIOS probing enabled. To verify whether NetBIOS probing is enabled, use the show running-config user-identity | include logout-probe command and verify that the command returns output.
The following example shows a Cisco ASA with NetBIOS probing enabled:ciscoasa# show running-config user-identity | include logout-probe
user-identity logout-probe netbios local-system
Note: The Cisco ASA Identity Firewall feature is enabled by default. However, NetBIOS probing is not.
Determining the Running Software Version
To determine whether a vulnerable version of Cisco ASA Software is running on an appliance, administrators can use the show version command. The following example shows the results for an appliance running Cisco ASA Software version 9.2(1):ciscoasa# show version | include Version
Cisco Adaptive Security Appliance Software Version 9.2(1)
Device Manager Version 7.4(1)
Customers who use Cisco Adaptive Security Device Manager (ASDM) to manage devices can locate the software version in the table that appears in the login window or the upper-left corner of the Cisco ASDM window.Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco Firepower Threat Defense software.
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There is a workaround that addresses this vulnerability. Customers can disable NetBIOS probing in the ASA software by entering the following commands at the enable prompt:
ciscoasa# configure terminal
ciscoasa(config)# no user-identity logout-probe netbios local-systemWhen NetBIOS probing is not enabled, as in the default configuration, the ASA software relies on an idle timeout mechanism to remove user-to-IP address mapping entries. NetBIOS probing is used to proactively determine if a user has logged out of the network, allowing the ASA software to remove the user-to-IP address mapping more quickly than if idle timeout is the only mechanism used for this purpose.
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Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html
Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.
When considering software upgrades, customers are advised to consult the Cisco Security Advisories and Responses archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC):
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.
In the following table, the left column lists major releases of Cisco ASA Software. The right column indicates whether a major release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability.
Cisco ASA Major Release First Fixed Release 7.21
Not Affected
8.01
Not Affected
8.11
Not Affected
8.21
Not Affected
8.31
Not Affected
8.41
Affected; migrate to 9.1(7.11) or later
8.51
Affected; migrate to 9.1(7.11) or later
8.61
Affected; migrate to 9.1(7.11) or later
8.71
Affected; migrate to 9.1(7.11) or later
9.0
9.0(4.42) or later
9.1 9.1(7.11) or later
9.2 9.2(4.17) or later
9.3 9.3(3.11) or later
9.4 9.4(3.11) or later
9.5
9.5(3.1) or later 9.6 9.6(2.1) or later
1Cisco ASA Software releases 7.2, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, and 8.7 have reached End of Software Maintenance. Customers should migrate to a supported release.
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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This vulnerability was reported to Cisco by Slipper and Kelwin (@KelwinYang) from Chaitin Technology Co., Ltd.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Version Description Section Status Date 1.1 Corrected the statement to reflect that a workaround is available Summary Final 2016-October-19 1.0 Initial public release. — Final 2016-October-19
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