Summary

• Multiple vulnerabilities exist in the Cisco ASA 5500 Series Adaptive Security Appliances and Cisco PIX Security Appliances. This security advisory outlines details of these vulnerabilities:

  • Windows NT Domain Authentication Bypass Vulnerability
    
  • IPv6 Denial of Service Vulnerability
    
  • Crypto Accelerator Memory Leak Vulnerability
    

  Note: These vulnerabilities are independent of each other. A device may be affected by one vulnerability and not affected by another.

  Cisco has released software updates that address these vulnerabilities. Workarounds that mitigate some of these vulnerabilities are available.

  This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20081022-asa.

Affected Products

• Vulnerable Products

  The following are the details about each vulnerability described within this advisory.

  Windows NT Domain Authentication Bypass Vulnerability

  Because of a Microsoft Windows NT Domain authentication issue the Cisco ASA and Cisco PIX devices may be susceptible to a VPN authentication bypass vulnerability. Cisco ASA or Cisco PIX security appliances that are configured for IPSec or SSL-based remote access VPN using Microsoft Windows NT Domain authentication may be vulnerable. Devices that are using any other type of external authentication (that is, LDAP, RADIUS, TACACS+, SDI, or local database) are not affected by this vulnerability.

  The following example demonstrates how Windows NT domain authentication is configured using the command line interface (CLI) on the Cisco ASA:

  aaa-server NTAuth protocol nt
   aaa-server NTAuth (inside) host 10.1.1.4
   nt-auth-domain-controller primary1

  Alternatively, to see if a device is configured for Windows NT Domain authentication use the show running-config | include nt-auth-domain-controller command.

  IPv6 Denial of Service Vulnerability

  Cisco ASA and Cisco PIX security appliances that are running software version 7.2(4)9 or 7.2(4)10 and configured for IPv6 may be vulnerable. This vulnerability does not affect devices configured only for IPv4.

  Note: IPv6 functionality is turned off by default.

  IPv6 is enabled on the Cisco ASA and Cisco PIX security appliance using the ipv6 address interface command. To verify if a device is configured for IPv6 use the show running-config | include ipv6 command.

  Alternatively, you can display the status of interfaces configured for IPv6 using the show ipv6 interface command in privileged EXEC mode, as shown in the following example:

  hostname# show ipv6 interface brief
  outside [up/up]
      unassigned
  inside [up/up]
      fe80::20d:29ff:fe1d:69f0
      fec0::a:0:0:a0a:a70
  dmz [up/up]
      unassigned

  In this example, the outside and dmz interfaces are not configured for IPv6.

  Crypto Accelerator Memory Leak Vulnerability

  Cisco ASA security appliances may experience a memory leak that can be triggered by a series of crafted packets. This memory leak occurs in the initialization code for the hardware crypto accelerator. Devices that are running software versions in the 8.0.x release are vulnerable.

  Note: Cisco ASA appliances that are running software versions in the 7.0, 7.1, and 7.2 releases are not vulnerable. The Cisco PIX security appliance is not affected by this vulnerability.

  Determination of Software Versions

  The show version command-line interface (CLI) command can be used to determine whether a vulnerable version of the Cisco PIX or Cisco ASA software is running. The following example shows a Cisco ASA Security Appliance that runs software release 8.0(4):

      ASA# show version
  
      Cisco Adaptive Security Appliance Software Version 8.0(4)
      Device Manager Version 6.0(1)
  
      [...]

  Customers who use the Cisco Adaptive Security Device Manager (ASDM) to manage their devices can find the version of the software displayed in the table in the login window or in the upper left corner of the ASDM window.

  Products Confirmed Not Vulnerable

  The Cisco Firewall Services Module (FWSM) is not affected by any of these vulnerabilities. Cisco PIX security appliances running versions 6.x are not vulnerable. No other Cisco products are currently known to be affected by these vulnerabilities.

Details

• This Security Advisory describes multiple distinct vulnerabilities. These vulnerabilities are independent of each other.

  Windows NT Domain Authentication Bypass Vulnerability

  Because of a Microsoft Windows NT Domain authentication issue the Cisco ASA and Cisco PIX devices may be susceptible to a VPN authentication bypass vulnerability. Cisco ASA or Cisco PIX security appliances configured for IPSec or SSL-based remote access VPN may be vulnerable.

  Note: Cisco ASA or Cisco PIX security appliances that are configured for IPSec or SSL-based remote access VPN using any other type of external authentication (that is, LDAP, RADIUS, TACACS+, SDI, or local database) are not affected by this vulnerability.

  The Cisco ASA security appliance supports Microsoft Windows server operating systems that support NTLM version 1, collectively referred to as "NT servers". NT Domain authentication is supported only for remote access VPNs.

  This vulnerability is documented in Cisco Bug ID CSCsu65735 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) identifiers CVE-2008-3815.

  IPv6 Denial of Service Vulnerability

  A specially crafted IPv6 packet may cause the Cisco ASA and Cisco PIX security appliances to reload. Devices that are running software version 7.2(4)9 or 7.2(4)10 and configured for IPv6 may be vulnerable. This vulnerability does not affect devices that are configured only for IPv4.

  Note: Devices that are running software versions in the 7.0, 7.1, 8.0, and 8.1 releases are not vulnerable.

  To configure IPv6 on a Cisco ASA or Cisco PIX security appliance, at a minimum, each interface needs to be configured with an IPv6 link-local address. Additionally, you can add a global address to the interface.

  Note: Only packets that are destined to the device (not transiting the device) may trigger the effects of this vulnerability. These packets must be destined to an interface configured for IPv6.

  This vulnerability is documented in Cisco Bug ID CSCsu11575 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2008-3816.

  Crypto Accelerator Memory Leak Vulnerability

  The Cisco ASA security appliances may experience a memory leak triggered by a series of packets. This memory leak occurs in the initialization code for the hardware crypto accelerator.

  Note: Only packets destined to the device (not transiting the device) may trigger this vulnerability.

  The following Cisco ASA features use the services the crypto accelerator provides, and therefore may be affected by this vulnerability:

  • Clientless WebVPN, SSL VPN Client, and AnyConnect Connections
    
  • ASDM (HTTPS) Management Sessions
    
  • Cut-Through Proxy for Network Access
    
  • TLS Proxy for Encrypted Voice Inspection
    
  • IP Security (IPsec) Remote Access and Site-to-site VPNs
    
  • Secure Shell (SSH) Access
    

  This vulnerability is documented in Cisco Bug ID CSCsj25896 ( registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) identifier CVE-2008-3817.

Workarounds

• This Security Advisory describes multiple distinct vulnerabilities. These vulnerabilities and their respective workarounds are independent of each other.

  Windows NT Domain Authentication Bypass Vulnerability

  LDAP authentication is not affected by this vulnerability. As a workaround, you can enable a different type of external authentication for Remote Access VPN instead of Windows NT Domain authentication.

  Note: For more information about support for a specific AAA server type, refer to the following link: http://www.cisco.com/en/US/docs/security/asa/asa80/configuration/guide/aaa.html#wp1069492

  IPv6 Denial of Service Vulnerability

  Customers that do not require IPv6 functionality on their devices can use the no ipv6 address interface sub-command to disable processing of IPv6 packets and eliminate their exposure

  Crypto Accelerator Memory Leak Vulnerability

  There are no workarounds for this vulnerability.

Fixed Software

• When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.

  In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center (TAC) or your contracted maintenance provider for assistance.

  The following list contains the first fixed software release of each vulnerability:

  Vulnerability	Affected Release	First Fixed Version
  Windows NT Domain Authentication Bypass Vulnerability	7.0	7.0(8)3
  	7.1	7.1(2)78
  	7.2	7.2(4)16
  	8.0	8.0(4)6
  	8.1	8.1(1)13
  IPv6 Denial of Service Vulnerability	7.0	Not Vulnerable
  	7.1	Not Vulnerable
  	7.2	7.2(4)11
  	8.0	Not Vulnerable
  	8.1	Not Vulnerable
  Crypto Accelerator Memory Leak Vulnerability	7.0	Not Vulnerable
  	7.1	Not Vulnerable
  	7.2	Not Vulnerable
  	8.0	8.0(4)
  	8.1	8.1(2)

  The following maintenance software releases are the first software releases that contain the fixes for the vulnerabilities mentioned in this Security Advisory:

  Fixed PIX software can be downloaded from:

  http://www.cisco.com/pcgi-bin/tablebuild.pl/pix?psrtdcat20e2

  Fix ASA software can be downloaded from:

  http://www.cisco.com/pcgi-bin/tablebuild.pl/asa?psrtdcat20e2

  For the "Windows NT Domain Authentication Bypass Vulnerability", only interim fixed software is currently available. Customers wishing to upgrade to a fixed version instead of applying a workaround may download PIX and ASA interim versions from:

  http://www.cisco.com/pcgi-bin/tablebuild.pl/PIXPSIRT?psrtdcat20e2

Exploitation and Public Announcements

• The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities described in this advisory.

  These vulnerabilities were found during internal testing and during the resolution of a technical support service request.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20081022-asa

Revision History

• Revision 1.0

  2008-October-22

  Initial public release

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