Summary

• Multiple vulnerabilities in the smart tunnel functionality of Cisco Adaptive Security Appliance (ASA) could allow an authenticated, local attacker to elevate privileges to the root user or load a malicious library file while the tunnel is being established.

  For more information about these vulnerabilities, see the Details section of this security advisory.

  Cisco has released software updates that address these vulnerabilities. There are no workarounds that address these vulnerabilities.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-asa-multi

Affected Products

• Vulnerable Products

  These vulnerabilities affect Cisco ASA Software.

  For information about which Cisco ASA Software releases are vulnerable, see the Fixed Software section of this advisory.

  Products Confirmed Not Vulnerable

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

Details

• Two vulnerabilities in the smart tunnel functionality of Cisco ASA could allow an authenticated, local attacker to elevate privileges to the root user or load a malicious library file during execution.

  The vulnerabilities are not dependent on one another; exploitation of one of the vulnerabilities is not required to exploit the other vulnerability. In addition, a software release that is affected by one of the vulnerabilities may not be affected by the other vulnerability.

  Details about the vulnerabilities are as follows.

  Cisco Adaptive Security Appliance Smart Tunnel Privilege Escalation Vulnerability

  A vulnerability in the smart tunnel functionality of Cisco ASA could allow an authenticated, local attacker to elevate privileges to the root user. This privilege escalation happens on a client device that attempts to establish a smart tunnel connection with the Cisco ASA. The escalation does not occur on the ASA itself.

  The vulnerability occurs because the Cisco ASA smart tunnel creates local system files on the client device with file permissions that are not restrictive enough. In addition, the ASA smart tunnel does not validate the system commands in these local system files before executing them. An attacker could exploit this vulnerability by running a malicious script on the client device when a valid user is establishing the Cisco ASA smart tunnel connection. A successful exploit could allow the attacker to elevate privileges to root on the client machine without the user's knowledge. The attacker needs valid device credentials on the local client device to exploit this vulnerability.

  The CVE ID for this vulnerability is: CVE-2019-1944

  Cisco Adaptive Security Appliance Smart Tunnel Library File Load Vulnerability

  A vulnerability in the smart tunnel functionality of Cisco ASA could allow an authenticated, local attacker to overwrite specific system files, which could then be loaded and executed during smart tunnel connection establishment. The attacker could take these actions on the client device that is attempting to establish the smart tunnel connection with the Cisco ASA and not on the ASA itself.

  The vulnerability occurs because the Cisco ASA can write files to specific locations on the file system, and the smart tunnel functionality does not validate the integrity of system files that load during execution. An attacker could exploit this vulnerability by creating a malicious system file and writing it to a specific location on the file system when a valid user is establishing the Cisco ASA smart tunnel connection. A successful exploit could allow the attacker to cause the smart tunnel to load a malicious executable. The attacker needs valid device credentials on the local client device to exploit this vulnerability.

  The CVE ID for this vulnerability is: CVE-2019-1945

Workarounds

• There are no workarounds that address these vulnerabilities.

Fixed Software

• Cisco has released free software updates that address the vulnerabilities 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 are advised to upgrade to an appropriate release as indicated in the applicable table in this section. In the following table(s), the left column lists Cisco software releases and the right column indicates whether a release is affected by the vulnerabilities described in this advisory and the release that includes the fix for these vulnerabilities.

  Cisco ASA Software

  Cisco ASA Software Release	First Fixed Release for These Vulnerabilities
  Earlier than 9.41	9.4.4.37
  9.4	9.4.4.37
  9.51	9.6.4.30
  9.6	9.6.4.30
  9.71	9.8.4.7
  9.8	9.8.4.7
  9.9	9.10.1.22
  9.10	9.10.1.22
  9.12	9.12.2.1

  1. Cisco ASA Software releases earlier than Release 9.4 and Cisco ASA Software Releases 9.5 and 9.7 have reached end of maintenance. Customers should migrate to a supported release that includes the fix for these vulnerabilities.

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.

Source

• Cisco would like to thank Francesco Giordano of Hacktive Security for reporting these vulnerabilities.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-asa-multi

Revision History

• Version	Description	Section	Status	Date
  1.1	Added a software version to the Fixed Releases table.	Fixed Software	Final	2019-August-29
  1.0	Initial public release.	-	Final	2019-August-07

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