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AUSCERT External Security Bulletin Redistribution
ESB-2020.3659
Cisco Adaptive Security Appliance Software SSL/TLS Denial of
Service Vulnerability
23 October 2020
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Adaptive Security Appliance Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-27124
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ssl-dos-7uZWwSEy
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Cisco Adaptive Security Appliance Software SSL/TLS Denial of Service
Vulnerability
Priority: High
Advisory ID: cisco-sa-asa-ssl-dos-7uZWwSEy
First Published: 2020 October 22 16:00 GMT
Version 1.0: Interim
Workarounds: No workarounds available
Cisco Bug IDs: CSCvt64822
CVE-2020-27124
CWE-457
Summary
o A vulnerability in the SSL/TLS handler of Cisco Adaptive Security Appliance
(ASA) Software could allow an unauthenticated, remote attacker to cause the
affected device to reload unexpectedly, leading to a denial of service
(DoS) condition.
The vulnerability is due to improper error handling on established SSL/TLS
connections. An attacker could exploit this vulnerability by establishing
an SSL/TLS connection with the affected device and then sending a malicious
SSL/TLS message within that connection. A successful exploit could allow
the attacker to cause the device to reload.
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-asa-ssl-dos-7uZWwSEy
Affected Products
o Vulnerable Products
This vulnerability affects Cisco ASA Software releases 9.13.1.12,
9.13.1.13, and 9.14.1.10 if they have a feature enabled that causes the
device to process SSL/TLS messages. These features include, but are not
limited to, the following:
AnyConnect SSL VPN ^ 1
Clientless SSL VPN ^ 1
HTTP server used for the management interface
1. Cisco Adaptive Security Virtual Appliances (ASAv) are not vulnerable for
these configurations.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine Whether a Device Could Process SSL or TLS Messages
To verify whether a device that is running Cisco ASA Software could process
SSL or TLS packets, use the show asp table socket | include SSL|DTLS
command and verify that it returns output. When this command returns any
output, the device is vulnerable. When 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 Cisco Firepower
Management Center (FMC) Software or Cisco Firepower Threat Defense (FTD)
Software.
Workarounds
o There are no workarounds that address this vulnerability.
Fixed Software
o 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 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.
Fixed Releases
Cisco has fixed this vulnerability in Cisco ASA releases 9.14.1.15 and
later. Cisco will fix this vulnerability in Cisco ASA Release 9.13.1.15 in
November 2020.
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-asa-ssl-dos-7uZWwSEy
Revision History
o +---------+---------------------------+---------+---------+--------------+
| Version | Description | Section | Status | Date |
+---------+---------------------------+---------+---------+--------------+
| 1.0 | Initial public release. | - | Interim | 2020-OCT-22 |
+---------+---------------------------+---------+---------+--------------+
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You have received this e-mail bulletin as a result of your organisation's
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maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
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and we will forward your request to the appropriate person.
NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
https://www.auscert.org.au/bulletins/
===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072
Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
===========================================================================
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