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AUSCERT External Security Bulletin Redistribution
ESB-2020.3645
Cisco Firepower 1000 Series Bleichenbacher Attack Vulnerability
23 October 2020
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Firepower 1000 Series
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Access Confidential Data -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-3585
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-tls-bb-2g9uWkP
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco Firepower 1000 Series Bleichenbacher Attack Vulnerability
Priority: Medium
Advisory ID: cisco-sa-asaftd-tls-bb-2g9uWkP
First Published: 2020 October 21 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvv13993
CVE-2020-3585
CWE-203
Summary
o A vulnerability in the TLS handler of Cisco Adaptive Security Appliance
(ASA) Software and Cisco Firepower Threat Defense (FTD) Software for Cisco
Firepower 1000 Series firewalls could allow an unauthenticated, remote
attacker to gain access to sensitive information.
The vulnerability is due to improper implementation of countermeasures
against the Bleichenbacher attack for cipher suites that rely on RSA for
key exchange. An attacker could exploit this vulnerability by sending
crafted TLS messages to the device, which would act as an oracle and allow
the attacker to carry out a chosen-ciphertext attack. A successful exploit
could allow the attacker to perform cryptanalytic operations that may allow
decryption of previously captured TLS sessions to the affected device.
To exploit this vulnerability, an attacker must be able to perform both of
the following actions:
Capture TLS traffic that is in transit between clients and the affected
device
Actively establish a considerable number of TLS connections to the
affected device
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-asaftd-tls-bb-2g9uWkP
Affected Products
o Vulnerable Products
At the time of publication, this vulnerability affected Cisco Firepower
1000 Series firewalls if they were running a vulnerable release of Cisco
ASA Software or FTD Software and had a feature enabled that caused the
device to process TLS messages. These features include, but are not limited
to, the following:
AnyConnect SSL VPN
Clientless SSL VPN
For information about which Cisco software releases were vulnerable at the
time of publication, see the Fixed Software section of this advisory. See
the Details section in the bug ID(s) at the top of this advisory for the
most complete and current information.
Determine Whether a Device Could Process SSL or TLS Messages
To determine whether a device that is running Cisco ASA Software or FTD
Software could process SSL or TLS packets, use the show asp table socket |
include SSL|DTLS command and verify that it returns output. If this command
returns any output, the device is vulnerable. If this command returns empty
output, the device is not affected by the vulnerability described in this
advisory. The following example shows the output of the show asp table
socket | include SSL|DTLS command from a device that is vulnerable:
ftd# show asp table socket | include SSL|DTLS
SSL 0005aa68 LISTEN x.x.x.x:443 0.0.0.0:*
SSL 002d9e38 LISTEN x.x.x.x:8443 0.0.0.0:*
DTLS 0018f7a8 LISTEN 10.0.0.250:443 0.0.0.0:*
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:
ASA Software that is running on any platform other than Cisco Firepower
1000 Series
FTD Software that is running on any platform other than Cisco Firepower
1000 Series
Firepower Management Center (FMC) Software
Workarounds
o There are no workarounds that address this vulnerability. However,
disabling use of TLS ciphers that rely on RSA for key exchange is a
possible mitigation.
Cisco ASA Software
To specify the TLS ciphers to be used on a device that is running Cisco ASA
Software, use the ssl cipher version custom command in global configuration
mode. Use a custom string to allow only cipher suites based on
Diffie-Hellman key exchange (DHE). Use the show ssl ciphers all command to
view the list of supported ciphers for each TLS version.
Cisco FTD Software
On devices that are running Cisco FTD Software and are managed through
Cisco FMC Software, TLS ciphers can be specified through Cisco FMC Software
under Devices > Platform Settings > [Edit | New Policy] > SSL > [Edit |
Add] . Then select a Custom security level and add the desired ciphers.
Cisco Firepower Device Manager (FDM) does not currently support the
selection of specific SSL/TLS ciphers or cipher suites.
Fixed Software
o When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories 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.
Fixed Releases
At the time of publication, the release information in the following table
(s) was accurate. See the Details section in the bug ID(s) at the top of
this advisory for the most complete and current information.
The left column lists Cisco software releases, and the right column
indicates whether a release was affected by the vulnerability described in
this advisory and which release included the fix for this vulnerability.
Cisco ASA Software
Cisco ASA Software Release First Fixed Release for This Vulnerability
Earlier than 9.13 ^1 Not applicable
9.13 9.13.1.13
9.14 9.14.1.30
1. Cisco ASA Software releases earlier than 9.13 do not support Cisco
Firepower 1000 Series firewalls.
Cisco FTD Software
Cisco FTD Software Release First Fixed Release for This Vulnerability
Earlier than 6.4.0 ^1 Not applicable
6.4.0 6.4.0.10
6.5.0 6.5.0.5 (future release)
6.6.0 6.6.1
1. Cisco FTD Software releases earlier than 6.4.0 do not support Cisco
Firepower 1000 Series firewalls.
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.
Exploitation and Public Announcements
o 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.
Source
o This vulnerability was found during the resolution of a Cisco TAC support
case.
Cisco Security Vulnerability Policy
o 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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-asaftd-tls-bb-2g9uWkP
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2020-OCT-21 |
+----------+---------------------------+----------+--------+--------------+
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