Cisco Security Advisory
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CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) code of Cisco ASA Software could allow an unauthenticated, remote attacker to cause a reload of the affected system.
The vulnerability is due to improper parsing of crafted SSL or TLS packets. An attacker could exploit this vulnerability by sending a crafted packet to the affected system.
Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems configured in routed and transparent firewall mode and in single or multiple context mode. This vulnerability can be triggered by IPv4 and IPv6 traffic. A valid SSL or TLS session is needed to exploit this vulnerability.
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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170419-asa-tls
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Vulnerable Products
This vulnerability affects Cisco ASA Software running on the following products:
- Cisco ASA 1000V Cloud Firewall
- Cisco ASA 5500 Series Adaptive Security Appliances
- Cisco ASA 5500-X Series Next-Generation Firewalls
- Cisco ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers
- Cisco Adaptive Security Virtual Appliance (ASAv)
- Cisco Firepower 9300 ASA Security Module
- Cisco ISA 3000 Industrial Security Appliance
Cisco ASA Software is affected if it processes SSL or TLS packets. There are multiple features that, when enabled, cause Cisco ASA Software to process this type of packet. These features include, but are not limited to, the following:
- AnyConnect and Clientless SSL VPN
- HTTP server used for the management interface
To verify whether an appliance running Cisco ASA Software could process SSL or TLS packets, use the show asp table socket | include SSL command and verify that it returns output. The following example shows a Cisco ASA appliance configured with Clientless SSL VPN and with the HTTP server enabled on the management interface and configured to listen on port 8443.
Determining the Running Software ReleaseBSNS-ASA5505-4# show asp table socket | include SSL
SSL 0005aa68 LISTEN x.x.x.x:443 0.0.0.0:*
SSL 002d9e38 LISTEN x.x.x.x:8443 0.0.0.0:*
To determine whether a vulnerable release of Cisco ASA Software is running on an appliance, administrators can use the show version command. The following example shows the results of the show version command on an appliance running Cisco ASA Software Release 9.2(1):
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 9.2(1)
Device Manager Version 7.4(1)Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this vulnerability.
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There are no workarounds that address this vulnerability.
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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_.htmlAdditionally, 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:
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.htmlCustomers 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
In the following table, the left column lists major releases of Cisco ASA Software. The right column indicates whether a major release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability.
Cisco ASA Software
Major Release
First Fixed Release Prior to 9.01
Affected, migrate to 8.4(7.31) or 9.1(7) or later
9.01
9.0(4.39) or later
9.1 9.1(7) or later
9.2
9.2(4.6) or later
9.31
9.3(3.8) or later
9.4 9.4(2) or later
9.5
9.5(2) or later
9.6 Not affected
9.7 Not affected
9.8 Not affected
1 Cisco ASA Software releases prior to 9.1 and Cisco ASA Software Release 9.3 have reached end-of-software maintenance. Customers should migrate to a supported release.
Note: It is possible that certain fixed software releases for this vulnerability are affected by a bug described in Cisco Field Notice FN-64291 where a security appliance may fail to pass traffic after 213 days of uptime. Customers should review this notice before determining a course of action for addressing the vulnerability described in this advisory. The issue described in the Cisco Field Notice is not a security vulnerability.
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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.
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This vulnerability was found during internal testing.
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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.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2017-April-19
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