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AUSCERT External Security Bulletin Redistribution
ESB-2022.0688.3
Cisco Email Security Appliance DNS Verification Denial of
Service Vulnerability
28 February 2022
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Cloud Email Security
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2022-20653
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-dos-MxZvGtgU
Comment: CVSS (Max): 7.5 CVE-2022-20653 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Revision History: February 28 2022: Fixed CVSS Max score
February 28 2022: Updated Fixed Software section to remove recommended releases
February 17 2022: Initial Release
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Cisco Email Security Appliance DNS Verification Denial of Service Vulnerability
Priority: High
Advisory ID: cisco-sa-esa-dos-MxZvGtgU
First Published: 2022 February 16 16:00 GMT
Last Updated: 2022 February 25 19:22 GMT
Version 1.1: Final
Workarounds: Yes
Cisco Bug IDs: CSCvy63674
CVE Names: CVE-2022-20653
CWEs: CWE-399
Summary
o A vulnerability in the DNS-based Authentication of Named Entities (DANE)
email verification component of Cisco AsyncOS Software for Cisco Email
Security Appliance (ESA) could allow an unauthenticated, remote attacker to
cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to insufficient error handling in DNS name
resolution by the affected software. An attacker could exploit this
vulnerability by sending specially formatted email messages that are
processed by an affected device. A successful exploit could allow the
attacker to cause the device to become unreachable from management
interfaces or to process additional email messages for a period of time
until the device recovers, resulting in a DoS condition. Continued attacks
could cause the device to become completely unavailable, resulting in a
persistent DoS condition.
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-esa-dos-MxZvGtgU
Affected Products
o Vulnerable Products
This vulnerability affects Cisco ESA devices if they are running a
vulnerable release of Cisco AsyncOS Software with the DANE feature enabled
and with the downstream mail servers configured to send bounce messages.
Note : The DANE feature is not enabled by default.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Cisco Cloud Email Security includes Cisco ESA and Cisco Secure Email and
Web Manager, formerly Cisco Security Management Appliance (SMA), as part of
the service solution. Cisco provides regular maintenance of the products
included in this solution. Customers can also request a software upgrade by
contacting Cisco Cloud Email Security support.
Attention : Simplifying the Cisco portfolio includes the renaming of
security products under one brand: Cisco Secure. For more information, see
Meet Cisco Secure .
Determine Whether DANE Is Configured
To determine whether DANE is configured, check the web UI page Mail
Policies > Destination Controls > Add Destination and verify whether the
DANE Support option is enabled.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Devices without the DANE feature enabled are not affected. Cisco has also
confirmed that this vulnerability does not affect the following Cisco
products:
Secure Email and Web Manager
Web Security Appliance (WSA)
Workarounds
o Customers may configure bounce messages from Cisco ESA instead of from
downstream dependent mail servers to prevent exploitation of this
vulnerability.
While this workaround has been deployed and was proven successful in a test
environment, customers should determine the applicability and effectiveness
in their own environment and under their own use conditions. Customers
should be aware that any workaround or mitigation that is implemented may
negatively impact the functionality or performance of their network based
on intrinsic customer deployment scenarios and limitations. Customers
should not deploy any workarounds or mitigations before first evaluating
the applicability to their own environment and any impact to such
environment.
Fixed Software
o Cisco has released free software updates that address the vulnerability
described in this advisory. Customers with service contracts that entitle
them to regular software updates should obtain security fixes through their
usual update channels.
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.
The Cisco Support and Downloads page on Cisco.com provides information
about licensing and downloads. This page can also display customer device
support coverage for customers who use the My Devices tool.
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
Customers are advised to upgrade to an appropriate fixed software release
as indicated in the following table(s):
Cisco AsyncOS Software Release First Fixed Release
12.5 and earlier Migrate to a fixed release.
13.0 Migrate to a fixed release.
13.5 Migrate to a fixed release.
14.0 14.0.2.020
The Cisco Product Security Incident Response Team (PSIRT) validates only
the affected and fixed release information that is documented in this
advisory.
Exploitation and Public Announcements
o The Cisco 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 Cesare Auteri, Steven Geerts, John-Paul Straver,
and Roy Wiss of Rijksoverheid Dienst ICT Uitvoering (DICTU) 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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-dos-MxZvGtgU
Revision History
o +---------+-----------------------------+----------+--------+-------------+
| Version | Description | Section | Status | Date |
+---------+-----------------------------+----------+--------+-------------+
| | Updated Fixed Software | | | |
| 1.1 | section to remove | Fixed | Final | 2022-FEB-25 |
| | recommended releases for | Software | | |
| | 13.0 and 13.5 trains. | | | |
+---------+-----------------------------+----------+--------+-------------+
| 1.0 | Initial public release. | - | Final | 2022-FEB-16 |
+---------+-----------------------------+----------+--------+-------------+
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