Summary

• A vulnerability in the authorization subsystem of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, but unprivileged (levels 0 and 1), remote attacker to perform privileged actions by using the web management interface.

  The vulnerability is due to improper validation of user privileges when using the web management interface. An attacker could exploit this vulnerability by sending specific HTTP requests via HTTPS to an affected device as an unprivileged user. An exploit could allow the attacker to retrieve files (including the running configuration) from the device or to upload and replace software images on the device.

  Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181219-asa-privesc

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ASA Software that is running on any Cisco product that has web management access enabled.

  Determine Whether Web Management Access Is Configured

  Administrators can use the show running-config http command to determine whether web management access is enabled. The following example shows the output of the command for a device that has the web management feature enabled and that allows access to the web management feature from the 10.10.10.0/24 network via the Management interface:

  ciscoasa# show running-config http
  
  http server enable
  http 10.10.10.0 255.255.255.0 Management

  Note: The device is vulnerable to requests only when they are sent from an IP address in the range configured in the http command.

  Determine the Cisco ASA Software Release

  To determine which Cisco ASA Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and refer to the output of the command. The following example shows the output of the command for a device that is running Cisco ASA Software Release 9.4(4):

  ciscoasa# show version | include Version
  
  Cisco Adaptive Security Appliance Software Version 9.4(4)
  Device Manager Version 7.4(1)
  .
  .
  .

  If a device is managed by using Cisco Adaptive Security Device Manager (ASDM), administrators can also determine which release is running on a device by referring to the release information in the table that appears in the Cisco ASDM login window or the Device Dashboard tab of the Cisco ASDM Home pane.

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

  Cisco has confirmed that Cisco Firepower Threat Defense (FTD) Software is not affected by this vulnerability.

Details

• This vulnerability could allow an authenticated but unprivileged (levels 0 and 1) user to perform privileged actions when command authorization is disabled on the Cisco ASA.

  When command authorization is not enabled, the ASA distinguishes only between unprivileged (levels 0 and 1) and privileged (levels 2 through 15) users. Privileged (levels 2 through 15) users are expected to have full administrative access to the ASA via the web management interface, even without knowing the enable password. Command authorization is disabled on the ASA by default.

  The “AAA and the Local Database” chapter in the Cisco ASA Configuration Guide provides further information.

Workarounds

• Enabling command authorization prevents exploitation of this vulnerability.

  Notes

  Enabling command authorization significantly changes the way that the Cisco ASA interprets privilege levels and authorizes actions. Before enabling the feature, administrators must clearly define which actions are allowed per privilege level using the privilege command in global configuration mode. Administrators should not enable command authorization using the aaa authorization command command until they have defined these actions.

  Administrators who use the Adaptive Security Device Manager (ASDM) to manage the ASA are advised to enable command authorization by using the ASDM because doing so will allow the ASDM to push predefined command sets for different privilege levels to the ASA. Having these command sets in place will ensure proper ASDM operation after command authorization is enabled.

  Further information about command authorization is in the “Management Access” chapter of the “System Administration” section in Cisco ASA Series General Operations CLI Configuration Guide and Cisco ASA Series General Operations ASDM Configuration Guide.

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 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 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

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

  Cisco ASA Software Release	First Fixed Release for CSCvm53531	Recommended Fixed Release for CSCvn65527
  Prior to 9.41	Migrate to 9.4.4.29	Migrate to 9.4.4.34
  9.4	9.4.4.29	9.4.4.34
  9.51	Migrate to 9.6.4.20	Migrate to 9.6.4.25
  9.6	9.6.4.20	9.6.4.25
  9.71	Migrate to 9.8.3.18	Migrate to 9.8.4
  9.8	9.8.3.18	9.8.4
  9.9	9.9.2.36	9.9.2.50
  9.10	9.10.1.7	9.10.1.17
  9.12	Not vulnerable	Not vulnerable

  ¹ Cisco ASA Software releases prior to Release 9.4 and Cisco ASA Software Releases 9.5 and 9.7 have reached end-of-software maintenance. Customers should migrate to a supported release.

  Customers can download the software from the Software Center on Cisco.com by clicking Browse all and navigating to Security > Firewalls > Adaptive Security Appliances (ASA) > ASA 5500-X Series Firewalls, where there is a list of Cisco ASA hardware platforms. Choose a platform, then choose Software on Chassis > Adaptive Security Appliance (ASA) Software. Most of these software releases are listed under Interim.

  Note: For the fix for CSCvm53531 to be effective, customers who have web management access enabled must ensure that the AAA configuration is accurate and complete. In particular, the aaa authentication http console {LOCAL | } command must be present. For further information, refer to the “About ASDM Authentication” section of the Cisco ASA Configuration Guide. The fix for CSCvn65527 no longer has this limitation.

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

• Cisco would like to thank Ken Johnson of Tenable, Inc. for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181219-asa-privesc

Revision History

• Version	Description	Section	Status	Date
  1.1	Added information about a more complete fix.	Fixed Releases	Final	2019-May-01
  1.0	Initial public release.	-	Final	2018-December-19

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