Cisco Adaptive Security Appliance Software Direct Authentication Denial of Service Vulnerability

Summary

• A vulnerability in the implementation of the direct authentication feature in Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause an affected device to unexpectedly reload, resulting in a denial of service (DoS) condition.
  
  The vulnerability is due to incomplete input validation of the HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to the local IP address of an affected device. A successful exploit could allow the attacker to cause the affected device to reload.
  
  Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems that have the direct authentication feature enabled. This vulnerability can be triggered by IPv4 or IPv6 traffic.
  
  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
  
  This advisory is available at the following link:
  https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20171004-asa

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Adaptive Security Appliance (ASA) Software that is running on the following Cisco products:
  

  • ASA 5500 Series Adaptive Security Appliances
  • ASA 5500-X Series Next-Generation Firewalls
  • ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers
  • ASA 1000V Cloud Firewall
  • Adaptive Security Virtual Appliance (ASAv)
  • Firepower 4110 Security Appliance
  • Firepower 9300 ASA Security Module
  • ISA 3000 Industrial Security Appliance

  For information about which software releases are vulnerable, see the Fixed Software section of this advisory.
  
  This vulnerability affects devices that are running a vulnerable release of Cisco ASA Software and have direct authentication enabled. The vulnerability only applies to HTTP access over the web management interface, telnet access with direct authentication is not vulnerable.
  

  
  Direct Authentication
  
  To determine whether direct authentication is enabled, administrators can use the show running-config | include aaa authentication listener command in the CLI and verify that the command returns output.
  
  The following example shows the output of the command for a device that is running Cisco ASA Software and has direct authentication enabled:
  

  ciscoasa# show running-config | include aaa authentication listener
  aaa authentication listener http inside port 5555

  For additional information, refer to the configuration example in the Direct Authentication section of the Cut-Through and Direct ASA Authentication Configuration Example document.
  
  Determining the Running Software Release

  To determine whether a vulnerable version of Cisco ASA Software is running on a device, administrators can use the show version command in the CLI. The following example shows the output of the command for a device that is running Cisco ASA Software Release 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 release 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 the following Cisco platforms:
  

  • Firepower 2100 Series Security Appliance
  • Firepower Threat Defense Software

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• 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: https://www.cisco.com/c/en/us/products/end-user-license-agreement.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 regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, 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.

  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 TAC: https://www.cisco.com/c/en/us/support/web/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.
  
  Fixed Releases
  
  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. Customers should upgrade to an appropriate release as indicated in this section.

  Cisco ASA Major Release	First Fixed Release
  Prior to 9.11	Affected, migrate to 9.1.7.17 or later
  9.1	9.1.7.17 or later
  9.2	9.2.4.20 or later
  9.31	Affected, migrate to 9.4.4.6
  9.4	9.4.4.6 or later
  9.51	9.5.3.9 or later
  9.6	9.6.3 or later
  9.7	9.7.1.8 or later
  9.8	9.8.1 or later

  ¹Cisco ASA Software releases prior to 9.1 and Cisco ASA releases 9.3 and 9.5 have reached End of Software Maintenance. Customers should migrate to a supported release.

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 resolution of a Cisco TAC support case.

URL

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20171004-asa

Revision History

• Version	Description	Section	Status	Date
  1.3	Updated the Fixed Releases table.	Fixed Software	Final	2017-October-12
  1.2	Metadata update.	-	Final	2017-October-10
  1.1	Corrected the show commands under Vulnerable Products to remove the quote characters.	Vulnerable Products	Final	2017-October-05
  1.0	Initial public release.	-	Final	2017-October-04

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