Cisco Security Advisory
Cisco Firepower 2100 Series SSL/TLS Inspection Denial of Service Vulnerability
A vulnerability in the SSL/TLS inspection of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 2100 Series firewalls could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
The vulnerability is due to improper input validation for certain fields of specific SSL/TLS messages. An attacker could exploit this vulnerability by sending a malformed SSL/TLS message through an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. No manual intervention is needed to recover the device after it has reloaded.
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:
This advisory is part of the October 2020 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication, which includes 17 Cisco Security Advisories that describe 17 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: October 2020 Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.
This vulnerability affects Cisco Firepower 2100 Series firewalls if they are running a vulnerable release of Cisco FTD Software and have the SSL/TLS inspection feature enabled.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine the Device Configuration
See the Firepower Management Center Configuration Guide for information about configuring SSL/TLS inspection policies.
To determine whether SSL/TLS inspection is enabled, choose one of the following options:
Option 1: Use the CLI
Use the show ssl-policy-config CLI command to determine whether SSL/TLS inspection is enabled on a device. The following example shows the output of the show ssl-policy-config command on a device that does not have an SSL policy configured and is not vulnerable:
> show ssl-policy-config
SSL policy not yet applied.
Any other output returned by the show ssl-policy-config command indicates that SSL/TLS inspection is configured and the device is vulnerable.
See the Cisco Firepower Threat Defense Command Reference for further information about the show ssl-policy-config command.
Option 2: Use the GUI
To verify whether SSL/TLS inspection is enabled on a device, navigate through the following menus:
- For devices managed by Firepower Management Center (FMC): Policies > Access Control > SSL
- For devices managed by Firepower Device Manager (FDM): Policies > SSL Decryption
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 this vulnerability does not affect the following Cisco products:
- Adaptive Security Appliance (ASA) Software
- Firepower Management Center (FMC) Software
- FTD Software that is running on any platform other than the platforms that are listed in the Vulnerable Products section of this advisory
There are no workarounds that address 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: 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.
In the following table(s), the left column lists Cisco software releases. The center column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. The right column indicates whether a release is affected by any of the vulnerabilities described in this bundle and which release includes fixes for those vulnerabilities.
Cisco FTD Software
Cisco FTD Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Bundle of Advisories Earlier than 6.2.21 Not vulnerable. Migrate to a fixed release. 6.2.2 Not vulnerable. Migrate to a fixed release. 6.2.3 Not vulnerable. Migrate to a fixed release. 6.3.0 Migrate to a fixed release. Migrate to a fixed release. 6.4.0 Migrate to a fixed release. Migrate to a fixed release. 6.5.0 Migrate to a fixed release. Migrate to a fixed release. 6.6.0 Not vulnerable. 6.6.1
1. Cisco FMC and FTD Software releases 6.0.1 and earlier, as well as releases 6.2.0 and 6.2.1, have reached end of software maintenance. Customers are advised to migrate to a supported release that includes the fix for this vulnerability.
To upgrade to a fixed release of Cisco FTD Software, do one of the following:
- For devices that are managed by using Cisco Firepower Management Center (FMC), use the FMC interface to install the upgrade. After installation is complete, reapply the access control policy.
- For devices that are managed by using Cisco Firepower Device Manager (FDM), use the FDM interface to install the upgrade. After installation is complete, reapply the access control policy.
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 found by Sanmith Prakash of Cisco during internal security testing.
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 1.0 Initial public release. - Final 2020-OCT-21
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products.