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             AUSCERT External Security Bulletin Redistribution

                               ESB-2015.2666
      Cisco ASA Software DHCPv6 Relay Denial of Service Vulnerability
                              22 October 2015

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Cisco ASA Software
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2015-6326  

Original Bulletin: 
   http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151021-asa-dns2

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Cisco Security Advisory

Cisco ASA Software DNS Denial of Service Vulnerability
High

Advisory ID:
cisco-sa-20151021-asa-dns2

Published:
2015 October 21 16:00  GMT

Version 1.0:
Final

CVSS Score:
Base - 7.1

Workarounds:
No workarounds available

Cisco Bug IDs:
CSCuu07799
CVE-2015-6326
CWE-399

Summary

    A vulnerability in the DNS code of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause an affected system to reload.

    The vulnerability is due to improper processing of DNS packets. An attacker could exploit this vulnerability by sending a crafted request to an affected Cisco ASA device to cause it to generate a DNS request packet. The attacker would need to spoof the reply packet with a crafted DNS response.

    Note: This vulnerability can be exploited only by traffic that is directed to the affected device. This vulnerability affects Cisco ASA Software configured in routed or transparent firewall mode and single or multiple context mode. This vulnerability can be triggered by IPv4 and IPv6 traffic.

    This vulnerability is documented in Cisco bug ID CSCuu07799 (registered customers only) and Common Vulnerabilities and Exposures (CVE) ID CVE-2015-6326.

    Cisco has released software updates that address this vulnerability. Workarounds that mitigate this vulnerability are not available. This advisory is available at the following link:
    http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151021-asa-dns2

Affected Products

    Cisco ASA Software running on the following products is affected by this vulnerability:
        Cisco ASA 1000V Cloud Firewall
        Cisco ASA 5500 Series Adaptive Security Appliances
        Cisco ASA 5500-X Series Next-Generation Firewalls
        Cisco ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers
        Cisco Adaptive Security Virtual Appliance (ASAv)
        Cisco FirePOWER 9300 ASA Security Module


    See the "Fixed Software" section of this security advisory for more information about the affected releases.
    Vulnerable Products
    Cisco ASA Software is affected by this vulnerability if at least one DNS server IP address is configured under a DNS server group. The address can be configured as part of the default DNS server group (DefaultDNS) or a user-defined DNS server group.

    To determine whether a DNS server IP address is configured, use the show running-config dns server-group command and verify that the name-server parameter includes an IP address.

    The following example shows a Cisco ASA device that is configured with the DNS server IP address 192.168.1.1 as part of the DefaultDNS server group.

        ciscoasa# show running-config dns server-group
        DNS server-group DefaultDNS
            name-server 192.168.1.1
        .
        .
        .

    Note: By default, the DNS name-server value is not configured in any DNS server group.

    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.
    Show Less

Indicators of Compromise

    No indicators of compromise are available for this vulnerability.

Workarounds

    There are no workarounds that mitigate this vulnerability. However, administrators may disable the affected feature.

Fixed Software

    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 upgrade 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.

    In the following table, the left column lists major releases of Cisco ASA Software. The center column indicates whether a major release is affected by the vulnerability described in this advisory and the first minor release that includes the fix for this vulnerability. The right column indicates whether a major release is affected by all the vulnerabilities described in the following advisories and which release includes fixes for those vulnerabilities:

        cisco-sa-20151021-asa-dhcp1
        cisco-sa-20150115-asa-dhcp
        cisco-sa-20151021-asa-dns1
        cisco-sa-20151021-asa-dns2
        cisco-sa-20151021-asa-ike


    Customers should upgrade to an appropriate release as indicated in the following table:

	Cisco ASA Major  	Fixed Release for This Advisory		First Fixed Release for All Advisories
	Release	First							in the October 2015 ASA Security	
									Advisory Bundled Publication  

	7.2  			Affected; migrate to 8.2(5.58) or later Affected; migrate to 8.2(5.58) or later 
	8.2  			8.2(5.58)  				8.2(5.58) and later 
	8.3  			Affected; migrate to 8.4(7.29) or later Affected; migrate to 8.4(7.29) or later 
	8.4  			8.4(7.29)  				8.4(7.29) 
	8.5  			Affected; migrate to 9.0(4.37) or later Affected; migrate to 9.0(4.37) or later 
	8.6  			Affected; migrate to 9.0(4.37) or later Affected; migrate to 9.0(4.37) or later 
	8.7  			8.7(1.17)  				8.7(1.17) and later 
	9.0  			9.0(4.37)  				9.0(4.37) and later 
	9.1  			9.1(6.6)  				9.1(6.8) and later 
	9.2   			9.2(4)   				9.2(4) and later 
	9.3  			9.3(3.5)  				9.3(3.5) and later 
	9.4    			9.4(1.5)  				9.4(2) and later 
	9.5   			Not affected  				Not affected 

    Software Download

    Cisco ASA Software can be downloaded from the Software Center on Cisco.com by visiting http://www.cisco.com/cisco/software/navigator.html.

    For Cisco ASA 5500 Series Adaptive Security Appliances and Cisco ASA 5500-X Next Generation Firewall, navigate to the following path. To find interim versions, click All Releases > Interim on the left side of the download page.

        Products > Security > Firewalls > Adaptive Security Appliances (ASA) > ASA 5500 Series Adaptive Security Appliances > <your Cisco ASA model> > Adaptive Security Appliance (ASA) Software 

    For the Cisco ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers, navigate to the following path. To find interim versions, click All Releases > Interim on the left side of the download page.

        Products > Cisco Interfaces and Modules > Services Modules > Catalyst 6500 Series / 7600 Series ASA Services Module > Adaptive Security Appliance (ASA) Software 

    For the Cisco ASA 1000V Cloud Firewall, navigate to the following path:

        Products > Security > Firewalls > Adaptive Security Appliances (ASA) > ASA 1000V Cloud Firewall 

    For the Cisco Adaptive Security Virtual Appliance (ASAv), navigate to the following path:

        Products > Security > Firewalls > Adaptive Security Appliances (ASA) > Adaptive Security Virtual Appliance (ASAv) > Adaptive Security Appliance (ASA) Software 

    For the Cisco FirePOWER 9300 ASA Module, navigate to the following path:

        Products > Security > Firewalls > Adaptive Security Appliances (ASA) > Firepower 9000 Series > Firepower 9300 Security Appliance >Adaptive Security Appliance (ASA) Software 

Exploitation and Public Announcements

    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.

Source

    This vulnerability was found during internal security tests.

URL

    http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151021-asa-dns2

Revision History

    Version 	Description 		Section Status 	Date
    1.0 	Initial public release. - 	Final 	2015-October-21

Legal Disclaimer

    THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

    A stand-alone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy, and may lack important information or contain factual errors. The information in this document is intended for end-users of Cisco products.

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