Summary

• A vulnerability in the web interface of the Cisco Adaptive Security Appliance (ASA) could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. It is also possible on certain software releases that the ASA will not reload, but an attacker could view sensitive system information without authentication by using directory traversal techniques.
  
  The vulnerability is due to lack of proper input validation of the HTTP URL. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device. An exploit could allow the attacker to cause a DoS condition or unauthenticated disclosure of information. This vulnerability applies to IPv4 and IPv6 HTTP traffic.
  
  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

  Note: Cisco continues to strongly recommend that customers upgrade to a fixed Cisco ASA Software release to remediate this vulnerability as there are continued attempts to exploit in the wild.
  
  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180606-asaftd

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ASA Software and Cisco Firepower Threat Defense (FTD) Software that is running on the following Cisco products:
  

  • 3000 Series Industrial Security Appliance (ISA)
  • ASA 1000V Cloud Firewall
  • 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
  • Adaptive Security Virtual Appliance (ASAv)
  • Firepower 2100 Series Security Appliance
  • Firepower 4100 Series Security Appliance
  • Firepower 9300 ASA Security Module
  • FTD Virtual (FTDv)

  ASA Software
  
  In the following table, the left column lists the Cisco ASA features that are potentially vulnerable. The right column indicates the basic configuration for the feature from the show running-config CLI command, if it can be determined. If the device is configured for one of these features, follow the additional instructions to determine if the device is vulnerable.
  
  

  Cisco ASA Feature	Possible Vulnerable Configuration
  Adaptive Security Device Manager (ASDM)1	http server enable <port> http <remote_ip_address> <remote_subnet_mask> <interface_name>
  AnyConnect IKEv2 Remote Access (with client services)	crypto ikev2 enable <interface_name> client-services port <port #> webvpn    anyconnect enable
  AnyConnect IKEv2 Remote Access (without client services)	crypto ikev2 enable <interface_name> webvpn    anyconnect enable
  AnyConnect SSL VPN	webvpn    enable <interface_name>
  Cisco Security Manager2	http server enable <port> http <remote_ip_address> <remote_subnet_mask> <interface_name>
  Clientless SSL VPN	webvpn    enable <interface_name>
  Cut-Through Proxy (Not vulnerable unless used in conjunction with other vulnerable features on the same port)	aaa authentication listener <interface_name> port <number>
  Local Certificate Authority (CA)	crypto ca server  no shutdown
  Mobile Device Manager (MDM) Proxy3	mdm-proxy   enable <interface_name>
  Mobile User Security (MUS)	webvpn  mus password <password>  mus server enable port <port #>  mus <address> <mask> <interface_name>
  Proxy Bypass	webvpn   proxy-bypass
  REST API4	rest-api image disk0:/<image name> rest-api agent

  ¹ASDM is vulnerable only from an IP address in the configured http command range.
  ² Cisco Security Manager is vulnerable only from an IP address in the configured http command range.
  ³The MDM Proxy is first supported as of Cisco ASA Software Release 9.3.1.
  ⁴The REST API is first supported as of Cisco ASA Software Release 9.3.2. The REST API is vulnerable only from an IP address in the configured http command range.
  
  Determining Whether an ASA Configured with a Potentially Vulnerable Feature Is Vulnerable
  
  Step 1: Administrators can use the show asp table socket | include SSL|DTLS command and look for a Secure Sockets Layer (SSL) or a Datagram Transport Layer Security (DTLS) listen socket on any TCP port. If either socket is present in the output and the ASA device is configured for one or more of the ASA features in the preceding table, the device may be vulnerable. The following example shows an ASA device with SSL and DTLS listen sockets:

  ciscoasa# show asp table socket | include SSL|DTLS

  SSL       00185038  LISTEN     172.16.0.250:443    0.0.0.0:*
  SSL       00188638  LISTEN     10.0.0.250:443      0.0.0.0:*
  DTLS      0018f7a8  LISTEN     10.0.0.250:443      0.0.0.0:*    

  Step 2: Administrators can then use the show processes | include Unicorn command to see if the vulnerable process is running on the device. This means that one of the possible vulnerable features has created an instance of the internal web server, which is vulnerable. If Unicorn Proxy Thread is present, the device is considered vulnerable.
  

  ciscoasa# show processes | include Unicorn

  Mwe 0x0000557f9f5bafc0 0x00007f62de5a90a8 0x0000557fa52b50a0       3632 0x00007f62c8c87030 30704/32768 Unicorn Proxy Thread 218

  Note: The Unicorn Proxy Thread identifier in the preceding example is 218 and can vary. A device must be considered vulnerable if the Unicorn Proxy Thread process is running, regardless of the actual thread identifier number.
  
  Determining the Running ASA Software Release
  
  To determine whether a vulnerable release of Cisco ASA Software is running on a device, administrators can use the show version | include 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)

  Administrators 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.
  
  FTD Software
  
  This vulnerability applies to all Cisco FTD Software releases except Release 6.2.0, which is not vulnerable. See the Fixed Releases section for additional information about fixed releases of Cisco FTD Software. The Cisco FTD Software release contains both Firepower and ASA code. Review the “Firepower Threat Defense Devices” section of the Cisco Firepower Compatibility Guide for additional information.
  
  In the following table, the left column lists the Cisco FTD features that are potentially vulnerable. The right column indicates the basic configuration for the feature from the show running-config CLI command, if it can be determined. If the device is configured for one of these features, follow the additional instructions to determine if the device is vulnerable.
  
  

  Cisco FTD Feature	Vulnerable Configuration
  HTTP Service enabled1	http server enable <port #> http <remote_ip_address> <remote_subnet_mask> <interface_name>
  AnyConnect IKEv2 Remote Access (with client services)2,3	crypto ikev2 enable <interface_name> client-services port <port #> webvpn   anyconnect enable
  AnyConnect IKEv2 Remote Access (without client services)2,3	crypto ikev2 enable <interface_name> webvpn   anyconnect enable
  AnyConnect SSL VPN2,3	webvpn   enable <interface_name>

  ¹ The HTTP feature is enabled via Firepower Threat Defense Platform Settings > HTTP in the Cisco Firepower Management Console (FMC).
  ² Remote Access VPN features are enabled via Devices > VPN > Remote Access in the Cisco FMC or via Device > Remote Access VPN in Cisco Firepower Device Manager (FDM).
  ³ Remote Access VPN features are first supported as of Cisco FTD Software Release 6.2.2.
  
  Determining Whether Cisco FTD Configured with a Potentially Vulnerable Feature Is Vulnerable
  
  Step 1: Administrators can use the show asp table socket | include SSL|DTLS command and look for an SSL or a DTLS listen socket on any TCP port. If either socket is present in the output and the FTD device is configured for one or more of the features listed in the preceding table, the device may be vulnerable. The following example shows an FTD device with SSL and DTLS listen sockets:

  firepower# show asp table socket | include SSL|DTLS

  SSL       01ffb648  LISTEN     1.1.1.1:443         0.0.0.0:* 
  DTLS      00009438  LISTEN     1.1.1.1:443         0.0.0.0:*   

  Step 2: Administrators can then use the show processes | include Unicorn command to see if the vulnerable process is running on the device. This means that one of the possible vulnerable features has created an instance of the internal web server, which is vulnerable. If Unicorn Proxy Thread is present, the device is considered vulnerable.
  

  firepower# show processes | include Unicorn

  Mwe 0x0000557f9f5bafc0 0x00007f62de5a90a8 0x0000557fa52b50a0       3632 0x00007f62c8c87030 30704/32768 Unicorn Proxy Thread 218

  Notes:

  • The Unicorn Proxy Thread identifier in the previous example is 218 and can vary. A device must be considered vulnerable if the Unicorn Proxy Thread process is running, regardless of the actual thread identifier number.
  • Although certain IKEv2 feature sets do not enable the underlying SSL TCP listening socket, they may still be vulnerable. Administrators can use the show running-config crypto ikev2 CLI command to check if the crypto ikev2 enable configuration command is present in the configuration, as shown in the following example:

    firepower# show running-config crypto ikev2 | include enable

    crypto ikev2 enable Outside

    If a command like crypto ikev2 enable is present in the running configuration and the anyconnect enable command is part of the global webvpn configuration, the Cisco FTD device is also considered vulnerable.

  
  Determining the Running Cisco FTD Software Release
  
  Administrators can use the show version command in the CLI to determine the Cisco FTD Software release. In this example, the device is running Release 6.2.2:
  

  > show version

  ---------------------[ ftd ]---------------------
  Model : Cisco ASA5525-X Threat Defense (75) Version 6.2.2 (Build 362)
  UUID : 2849ba3c-ecb8-11e6-98ca-b9fc2975893c
  Rules update version : 2017-03-15-001-vrt
  VDB version : 279
  ----------------------------------------------------

  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 AnyConnect Secure Mobility Client is not vulnerable.

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 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 tables.

  Cisco ASA Software

  Cisco ASA Software Release	First Fixed Release for This Vulnerability
  Prior to 9.11	Migrate to 9.1.7.29
  9.1	9.1.7.29
  9.2	9.2.4.33
  9.31	Migrate to 9.4.4.18
  9.4	9.4.4.18
  9.51	Migrate to 9.6.4.8
  9.6	9.6.4.8
  9.7	9.7.1.24
  9.8	9.8.2.28
  9.9	9.9.2.1

  ¹Cisco ASA Software releases prior to Release 9.1 and Cisco ASA Software Releases 9.3 and 9.5 have reached end-of-software maintenance. Customers should migrate to a supported release.
  
  The software is available for download from the Software Center on Cisco.com by navigating to Products > Security > Firewalls > Adaptive Security Appliances (ASA) > ASA 5500-X Series Firewalls, where there is a list of Cisco ASA hardware platforms. The majority of these software releases are listed under Interim.

  Cisco FTD Software

  Cisco FTD Software Release	First Fixed Release for This Vulnerability
  6.0	Migrate to 6.1.0 HotFix or later
  6.0.1	Migrate to 6.1.0 HotFix or later
  6.1.0	Cisco_FTD_Hotfix_EI-6.1.0.7-2.sh (all FTD hardware platforms except 41xx and 9300) Cisco_FTD_SSP_Hotfix_EI-6.1.0.7-2.sh (41xx and 9300 FTD hardware platforms)
  6.2.0	Not vulnerable
  6.2.1	Migrate to 6.2.2.3
  6.2.2	6.2.2.3
  6.2.3	6.2.3.1 6.2.3-851 6.2.3-85.02

  ¹Software image for FTD Virtual for the Microsoft Azure Cloud
  ²Software image for FTD Virtual for the AWS Cloud
  
  The software is available for download from the Software Center on Cisco.com by navigating to Products > Security > Firewalls > Next-Generation Firewalls (NGFW), where there is a list of Cisco FTD hardware platforms.

Exploitation and Public Announcements

• In September 2019, the Cisco Product Security Incident Response Team (PSIRT) became aware of additional attempted exploitation of this vulnerability in the wild. Cisco continues to strongly recommend that customers upgrade to a fixed Cisco ASA Software release to remediate this vulnerability.

Source

• Cisco would like to thank security researcher Michal Bentkowski from Securitum for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180606-asaftd

Revision History

• Version	Description	Section	Status	Date
  1.4	Changed the SIR value to Critical, added a note about upgrading to the Summary, and updated the exploitation information in the Exploitation and Public Announcements section.	SIR, Summary, Exploitation and Public Announcements	Final	2019-September-24
  1.3	Updated the exploitation information in the Exploitation and Public Announcements section.	Exploitation and Public Announcements	Final	2019-March-06
  1.2	Corrected advisory metadata to remove unaffected version 6.2.0.	—	Final	2018-October-05
  1.1	Updated the Exploitation and Public Announcements section with up-to-date exploitation information.	Exploitation and Public Announcements	Final	2018-June-22
  1.0	Initial public release.	—	Final	2018-June-06

  Show Less