Cisco ASA Software VPN ISAKMP Denial of Service Vulnerability

Summary

• A vulnerability in the Internet Key Exchange (IKE) version 1 (v1) 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 handling of Internet Security Association and Key Management Protocol (ISAKMP) packets. An attacker could exploit this vulnerability by sending crafted UDP packets to the affected system. A successful exploit could allow the attacker to cause an affected system to reload.
  
  Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems configured in routed firewall mode only and in single or multiple context mode. This vulnerability can be triggered by IPv4 and IPv6 traffic.
  
  This vulnerability is documented in Cisco bug ID CSCus94026 (registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2015-6327.
  
  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-ike

Affected Products

• Cisco ASA Software running on the following products is affected by this vulnerability:
  

  • 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 ASA 1000V Cloud Firewall
  • Cisco Adaptive Security Virtual Appliance (ASAv)

  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 the system is configured to terminate IKEv1 VPN connections.
  
  This includes the following:
  

  • LAN-to-LAN using IKEv1
  • Remote Access VPN using the IPSec VPN client
  • Layer 2 Tunneling Protocol (L2TP)-over-IPSec VPN connections

  Cisco ASA Software is not affected by this vulnerability if the system is configured to terminate the following VPN connections:
  

  • Clientless SSL
  • AnyConnect SSL
  • IKEv2 AnyConnect
  • IKEv2 LAN-to-LAN

  To determine whether the Cisco ASA is configured to terminate IKEv1 VPN connections, a crypto map should be configured for at least one interface. Administrators should use the show running-config crypto map | include interface command and verify that it returns output. The following example shows a crypto map called cmap configured on the outside interface:
  

  ciscoasa# show running-config crypto map | include interface
  
  crypto map outside_map interface outside
  
  
  

  Additionally IKEv1 should also be enabled on that interface. This can be determined by using the show running-config crypto ikev1 command, or show running-config | include crypto isakmp enable command for Cisco ASA Software releases prior to 8.4, and verifying that ikev1 is enabled on the interface.
  
  The following example shows IKEv1 enabled on the outside interface:
  

  ciscoasa# show running-config crypto ikev1 
  
  crypto ikev1 enable outside
  
  
  

  Note: IKEv1 is not configured by default.
  
  

  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

  Cisco FirePOWER 9300 ASA Security Module is not affected by this vulnerability
  
  No other Cisco products are currently known to be affected by this vulnerability.
  

Indicators of Compromise

• A Cisco ASA device reloading with thread name IKE Daemon may indicate exploitation of this vulnerability.
  
  The thread name is listed at the beginning of the crashinfo file. The crashinfo file can be accessed by using the show crashinfo command. The following example shows a crashinfo file with thread name IKE Daemon:
  

  ciscoasa# show crashinfo 
  
  : Saved_Crash
  
  
  Thread Name: IKE Daemon
  
  .
  .
  . 

  Customers should contact their support organization if they suspect active exploitation of this vulnerability to have the traceback decoded to confirm whether the crash is due to 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 Release	First Fixed Release for This Vulnerability	First Fixed Release for All Vulnerabilities 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(6.8)	9.1(6.8) and later
  9.2	9.2(4)	9.2(4) and later
  9.3	9.3(3)	9.3(3.6) and later
  9.4	Not affected	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 > > 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-ike

Revision History

• Version	Description	Section	Status	Date
  1.1	Corrected recommended release version for Cisco ASA 9.3 train.	Fixed Software	Final	2015-November-12
  1.0	Initial public release.	-	Final	2015-October-21

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