A vulnerability in the Deterministic Random Bit Generator (DRBG), also known as Pseudorandom Number Generator (PRNG), used in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a cryptographic collision, enabling the attacker to discover the private key of an affected device. The vulnerability is due to insufficient entropy in the DRBG when generating cryptographic keys. An attacker could exploit this vulnerability by generating a large number of cryptographic keys on an affected device and looking for collisions with target devices. A successful exploit could allow the attacker to impersonate an affected target device or to decrypt traffic secured by an affected key that is sent to or from an affected target device. Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability. This advisory is available at the following link: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190501-asa-ftd-entropy
Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190501-asa-ftd-entropy
This vulnerability affects the following Cisco products that are running Cisco ASA Software Releases 9.8 or 9.9 or FTD Software Releases 6.2.1, 6.2.2, or 6.2.3:
Note: Devices running other releases of Cisco ASA Software or FTD Software may also be vulnerable if they are configured with at least one of the following:
If no Trustpoint is configured and no RSA key pair for use with SSH Access is present, a device is vulnerable only while running an affected release.
For information about which Cisco ASA Software and FTD Software releases are vulnerable, see the Fixed Software section of this advisory.
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.
| Cisco ASA Feature |
Possible Vulnerable Configuration |
|---|---|
| Adaptive Security Device Manager (ASDM)1 |
http server enable http |
| AnyConnect SSL VPN | webvpn enable |
| Cisco Security Manager1 | http server enable http |
| Clientless SSL VPN (WebVPN) | webvpn enable |
| IKEv1 VPN (Remote Access and LAN-to-LAN) using Certificate-based Authentication |
crypto ikev1 enable crypto ikev1 policy authentication rsa-sig tunnel-group trust-point |
| IKEv2 VPN (Remote Access and LAN-to-LAN) using Certificate-based Authentication |
crypto ikev2 enable tunnel-group ikev2 remote-authentication certificate ikev2 local-authentication certificate |
| Local Certificate Authority (CA) | crypto ca server no shutdown |
| Mobile Device Manager (MDM) Proxy |
mdm-proxy enable |
| Mobile User Security (MUS) |
webvpn mus password mus server enable port mus |
| Proxy Bypass | webvpn proxy-bypass |
| REST API1 | rest-api image disk0:/ rest-api agent |
| SSH Access2 |
ssh |
FTD Software
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.
| Cisco FTD Feature | Possible Vulnerable Configuration |
|---|---|
| AnyConnect SSL VPN1,2 | webvpn enable |
| Clientless SSL VPN (WebVPN)2 | webvpn enable |
| HTTP Service enabled3,4 | http server enable http |
| IKEv1 VPN (Remote Access and LAN-to-LAN) using Certificate-based Authentication1,2 |
crypto ikev1 enable crypto ikev1 policy authentication rsa-sig tunnel-group trust-point |
| IKEv2 VPN (Remote Access and LAN-to-LAN) using Certificate-based Authentication1,2 |
crypto ikev2 enable tunnel-group ikev2 remote-authentication certificate ikev2 local-authentication certificate |
| SSH Service5 |
ssh |
To determine which Cisco ASA Software release is running on a device, administrators can log in to the device, use the show version | include Version command in the CLI, and refer to the output of the command. The following example shows the output of the command for a device that is running Cisco ASA Software Release 9.9.2.18:
Vulmon
ciscoasa# show version | include Version
Cisco Adaptive Security Appliance Software Version 9.9.2.18
Device Manager Version 7.4(1)
.
.
.
If a device is managed by using Cisco Adaptive Security Device Manager (ASDM), administrators can also determine which release is running on a device by referring to the release information in the table that appears in the Cisco ASDM login window or the Device Dashboard tab of the Cisco ASDM Home pane.
To determine which Cisco FTD Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and refer to the output of the command. The following example shows the output of the command for a device that is running Cisco FTD Software Release 6.2.0:
> show version
---------------------[ ftd ]---------------------
Model : Cisco ASA5525-X Threat Defense (75) Version 6.2.0 (Build 362)
UUID : 2849ba3c-ecb8-11e6-98ca-b9fc2975893c
Rules update version : 2017-03-15-001-vrt
VDB version : 279
----------------------------------------------------
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 Cisco ASA Software or FTD Software running on the following platforms:
To avoid the use of potentially weak cryptographic keys, administrators can generate a key pair and a corresponding certificate on a trusted device outside of the Cisco ASA or FTD device and then import the base 64 encoded PKCS #12 file containing the keys and certificate(s) to the Cisco ASA or FTD device using the crypto ca import
See the ASA 8.x: Renew and Install the SSL Certificate with ASDM tech note for further details, including steps for how to accomplish this task via the Cisco Adaptive Security Device Manager (ASDM).
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 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.
Customers are advised to upgrade to an appropriate release as indicated in the applicable table in this section. To ensure a complete upgrade solution, customers should consider that this advisory is part of a collection that includes the following advisories:
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 release that includes the fix for this vulnerability. The right column indicates whether a release is affected by all the vulnerabilities described in this collection of advisories and which release includes fixes for those vulnerabilities.
Note: After upgrading to a fixed release, administrators must re-generate all RSA and ECDSA key pairs that were generated on an affected device while running a vulnerable release.
Cisco ASA Software
| Cisco ASA Software Release |
Recommended Release for This Vulnerability |
Recommended Release for All Vulnerabilities Described in the Collection of Advisories |
|---|---|---|
| Prior to 9.41 |
Not vulnerable |
9.4.4.34 |
| 9.4 | Not vulnerable |
9.4.4.34 |
| 9.51 | Not vulnerable |
9.6.4.25 |
| 9.6 | Not vulnerable | 9.6.4.25 |
| 9.71 | Not vulnerable | 9.8.4 |
| 9.8 | 9.8.4 |
9.8.4 |
| 9.9 | 9.9.2.50 | 9.9.2.50 |
| 9.10 | Not vulnerable |
9.10.1.17 |
| 9.12 | Not vulnerable | Not vulnerable |
Cisco FTD Software
| Cisco FTD Software Release |
Recommended Release for This Vulnerability |
Recommended Release for All Vulnerabilities Described in the Collection of Advisories |
|---|---|---|
| 6.0 | Not vulnerable | 6.2.3.12 |
| 6.0.1 | Not vulnerable | 6.2.3.12 |
| 6.1.0 | Not vulnerable | 6.2.3.12 |
| 6.2.0 | Not vulnerable | 6.2.3.12 |
| 6.2.1 | 6.2.3.12 |
6.2.3.12 |
| 6.2.2 | 6.2.3.12 |
6.2.3.12 |
| 6.2.3 | 6.2.3.12 | 6.2.3.12 |
| 6.3.0 | 6.3.0.3 |
6.3.0.3 |
| 6.4.0 | Not vulnerable | Not vulnerable |
To upgrade to a fixed release of Cisco FTD Software, customers can do one of the following:
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.
Cisco would like to thank Greg Zaverucha of Microsoft for reporting this vulnerability.
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 the FTD fixed releases table to indicate that FTD Software Release 6.3.0.3 is available. | Fixed Software | Final | 2019-May-02 |
| 1.0 | Initial public release. | - | Final | 2019-May-01 |
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