A vulnerability in the Secure Sockets Layer (SSL) Virtual Private Network (VPN) Client Certificate Authentication feature for Cisco Adaptive Security Appliance (ASA) could allow an unauthenticated, remote attacker to establish an SSL VPN connection and bypass certain SSL certificate verification steps. The vulnerability is due to incorrect verification of the SSL Client Certificate. An attacker could exploit this vulnerability by connecting to the ASA VPN without a proper private key and certificate pair. A successful exploit could allow the attacker to establish an SSL VPN connection to the ASA when the connection should have been rejected. 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-20180418-asa1
To be considered vulnerable, the ASA or FTD has to be configured for Client Certificate Authentication. Administrators can check for a vulnerable configuration using the show running-config tunnel-group | include authentication | include certificate command. If either the authentication certificate or authentication multiple-certificate configuration option is present in the configuration then the device is vulnerable. The following is an example of a vulnerable configuration:
Vulmon
asa# show running-config tunnel-group | include authentication | include certificate
authentication certificate
authentication multiple-certificate
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.ciscoasa# show version | include Version
Cisco Adaptive Security Appliance Software Version 9.4(4)
Device Manager Version 7.4(1)
> show version
---------------------[ ftd ]---------------------
Model : Cisco ASA5525-X Threat Defense (75) Version 6.1.0 (Build 362)
UUID : 2849ba3c-ecb8-11e6-98ca-b9fc2975893c
Rules update version : 2017-03-15-001-vrt
VDB version : 279
----------------------------------------------------
No other Cisco products are currently known to be affected by this vulnerability.
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: http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.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: http://www.cisco.com/en/US/support/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.
| Cisco ASA Major Release |
Recommended Fixed Release for This Vulnerability | Recommended Fixed Release for All the Vulnerabilities Described in the Collection of Advisories |
|---|---|---|
| Prior to 9.11 | Not vulnerable | 9.1.7.20 |
| 9.1 | Not vulnerable | 9.1.7.20 |
| 9.2 | Not vulnerable | 9.2.4.27 |
| 9.31 | Not vulnerable | 9.4.4.14 |
| 9.4 | 9.4.4.14 or later |
9.4.4.14 |
| 9.51 |
Migrate to 9.6.3.20 |
9.6.4.6 |
| 9.6 | 9.6.3.20 or later |
9.6.4.6 |
| 9.7 | Not vulnerable | 9.7.1.24 |
| 9.8 | Not vulnerable | 9.8.2.28 |
| 9.9 | Not vulnerable | 9.9.2.1 |
1Cisco ASA Software releases prior to 9.1 and ASA 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 Cisco Software Center by navigating to Products > Security > Firewalls > Adaptive Security Appliances (ASA) > ASA 5500-X Series Firewalls where there is a list of ASA hardware platforms. The majority of these software releases are listed under Interim.
| Cisco FTD Major Release |
Recommended Fixed Release for This Vulnerability | Recommended Fixed Release for All the Vulnerabilities Described in the Collection of Advisories |
|---|---|---|
| 6.0 | Migrate to 6.1.0.6 |
Cisco_FTD_SSP_Hotfix_EI-6.1.0.7-2.sh (41xx and 9300 FTD hardware platform) Cisco_FTD_Hotfix_EI-6.1.0.7-2.sh (All FTD hardware platforms except 41xx and 9300) |
| 6.0.1 | Migrate to 6.1.0.6 |
Cisco_FTD_SSP_Hotfix_EI-6.1.0.7-2.sh (41xx and 9300 FTD hardware platform) Cisco_FTD_Hotfix_EI-6.1.0.7-2.sh (All FTD hardware platforms except 41xx and 9300) |
| 6.1.0 |
6.1.0.6 or later |
Cisco_FTD_SSP_Hotfix_EI-6.1.0.7-2.sh (41xx and 9300 FTD hardware platform) Cisco_FTD_Hotfix_EI-6.1.0.7-2.sh (All FTD hardware platforms except 41xx and 9300) |
| 6.2.0 |
Not vulnerable |
6.2.0.5 |
| 6.2.1 |
Not vulnerable | Cisco_FTD_SSP_Hotfix_BD-6.2.2.3-4.sh.REL.tar (41xx and 9300 FTD hardware platforms) Cisco_FTD_SSP_FP2K_Hotfix_BD-6.2.2.3-4.sh.REL.tar (21xx FTD hardware platform) Cisco_FTD_Hotfix_BD-6.2.2.3-4.sh.REL.tar (All other FTD hardware platforms) |
| 6.2.2 |
Not vulnerable |
Cisco_FTD_SSP_Hotfix_BD-6.2.2.3-4.sh.REL.tar (41xx and 9300 FTD hardware platforms) Cisco_FTD_SSP_FP2K_Hotfix_BD-6.2.2.3-4.sh.REL.tar (21xx FTD hardware platform) Cisco_FTD_Hotfix_BD-6.2.2.3-4.sh.REL.tar (All other FTD hardware platforms) |
| 6.2.3 | Not vulnerable |
Cisco_FTD_SSP_Hotfix_A-6.2.3.1-10.sh.REL.tar (41xx and 9300 FTD hardware platforms) Cisco_FTD_SSP_FP2K_Hotfix_A-6.2.3.1-10.sh.REL.tar (21xx FTD hardware platform) Cisco_FTD_Hotfix_A-6.2.3.1-10.sh.REL.tar (All other FTD hardware platforms) |
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.
This vulnerability was resolved during resolution of a Cisco TAC Support case.
To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.1 | Updated metadata. No text changes. | None | Final | 2018-April-27 |
| 1.0 | Initial public release | - | Final | 2018-April-18 |
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