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AUSCERT External Security Bulletin Redistribution
ESB-2023.6367
Cisco Adaptive Security Appliance Software and Firepower Threat Defense
Software Remote Access SSL VPN Multiple Certificate
Authentication Bypass Vulnerability
2 November 2023
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Adaptive Security Appliance Software
Firepower Threat Defense Software
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2023-20247
Original Bulletin:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-multi-cert-dzA3h5PT
Comment: CVSS (Max): 5.0 CVE-2023-20247 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N
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Cisco Adaptive Security Appliance Software and Firepower Threat Defense
Software Remote Access SSL VPN Multiple Certificate Authentication Bypass
Vulnerability
Priority: Medium
Advisory ID: cisco-sa-asaftd-multi-cert-dzA3h5PT
First Published: 2023 November 1 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCwe20918
CVE Names: CVE-2023-20247
Summary
o A vulnerability in the remote access SSL VPN feature of Cisco Adaptive
Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD)
Software could allow an authenticated, remote attacker to bypass a
configured multiple certificate authentication policy and connect using
only a valid username and password.
This vulnerability is due to improper error handling during remote access
VPN authentication. An attacker could exploit this vulnerability by sending
crafted requests during remote access VPN session establishment. A
successful exploit could allow the attacker to bypass the configured
multiple certificate authentication policy while retaining the privileges
and permissions associated with the original connection profile.
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-asaftd-multi-cert-dzA3h5PT
This advisory is part of the November 2023 release of the Cisco ASA, FTD,
and FMC Security Advisory Bundled publication. For a complete list of the
advisories and links to them, see Cisco Event Response: November 2023
Semiannual Cisco ASA, FMC, and FTD Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
At the time of publication, this vulnerability affected Cisco devices if
they were running a vulnerable release of Cisco ASA Software or FTD
Software and had the remote access SSL VPN feature enabled with at least
one configuration profile requiring multiple certificate authentication.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine the Remote Access SSL VPN Configuration
To determine the remote access VPN configuration, use the show
running-config webvpn | include ^ enable CLI command. If the command
returns output, the remote access SSL VPN feature is enabled on the listed
interface(s). Empty output indicates that the remote access SSL VPN feature
is not enabled. The following example shows the output of the show
running-config webvpn | include ^ enable command on a device that has the
remote access SSL VPN feature enabled on the outside interface:
asa# show running-config webvpn | include ^ enable
enable outside
If the remote access SSL VPN feature is enabled on at least one interface,
use the show running-config tunnel-group | include multiple-certificate CLI
command to assess whether a connection profile requiring multiple
certificate authentication is configured. If the command returns output, at
least one configuration profile requiring multiple certificate
authentication is configured. Empty output indicates that multiple
certificate authentication is not used on the device. The following example
shows the output of the show running-config tunnel-group | include
multiple-certificate command on a device that has one configuration profile
requiring multiple certificate authentication configured:
asa# show running-config tunnel-group | include multiple-certificate
authentication multiple-certificate
If one or both of the above commands return empty output, the device is not
affected by this vulnerability.
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:
Firepower Management Center (FMC) Software
IOS Software
IOS XE Software
IOS XR Software
Next-Generation Intrusion Prevention System (NGIPS) Software
NX-OS Software
Workarounds
o There are no workarounds that address this vulnerability.
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.
Cisco ASA, FMC, and FTD Software
To help customers determine their exposure to vulnerabilities in Cisco ASA,
FMC, and FTD Software, Cisco provides the Cisco Software Checker . This
tool identifies any Cisco security advisories that impact a specific
software release and the earliest release that fixes the vulnerabilities
that are described in each advisory ("First Fixed"). If applicable, the
tool also returns the earliest release that fixes all the vulnerabilities
that are described in all the advisories that the Software Checker
identifies ("Combined First Fixed").
To use the tool, go to the Cisco Software Checker page and follow the
instructions. Alternatively, use the following form to search for
vulnerabilities that affect a specific software release. To use the form,
follow these steps:
1. Choose which advisories the tool will search-all advisories, only
advisories with a Critical or High Security Impact Rating (SIR) , or
only this advisory.
2. Choose the appropriate software.
3. Choose the appropriate platform.
4. Enter a release number-for example, 9.16.2.11 for Cisco ASA Software or
6.6.7 for Cisco FTD Software.
5. Click Check .
[2 ] [ ] [Critical,High,Medium]
[Only this advisory ] [Cisco ASA Software]
[Any Platform ]
[ ] [Check]
For instructions on upgrading your FTD device, see Cisco Firepower
Management Center Upgrade Guide .
Additional Resources
For help determining the best Cisco ASA, FTD, or FMC Software release, see
the following Recommended Releases documents. If a security advisory
recommends a later release, Cisco recommends following the advisory
guidance.
Cisco ASA Compatibility
Cisco Secure Firewall ASA Upgrade Guide
Cisco Secure Firewall Threat Defense Compatibility Guide
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 Cisco would like to thank Tobias Moritz of Deutsche Telekom MMS GmbH for
reporting this vulnerability.
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.
Subscribe to Cisco Security Notifications
o Subscribe
Related to This Advisory
o Cisco Event Response: November 2023 Cisco ASA, FMC, and FTD Software
Security Advisory Bundled Publication
URL
o https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-multi-cert-dzA3h5PT
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2023-NOV-01 |
+----------+---------------------------+----------+--------+--------------+
Legal Disclaimer
o 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.
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