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AUSCERT External Security Bulletin Redistribution
ESB-2022.4843
Cisco IOS XE Wireless Controller Software for the Catalyst 9000 Family DHCP
Processing Denial of Service Vulnerability
29 September 2022
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AusCERT Security Bulletin Summary
---------------------------------
Product: Catalyst 9800-CL Wireless Controllers for Cloud
Catalyst 9300,9400 Embedded Wireless Controller
9500 Series Switches
Catalyst 9800 Series Wireless Controllers
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2022-20847
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-wlc-dhcp-dos-76pCjPxK
Comment: CVSS (Max): 8.6 CVE-2022-20847 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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:C/C:N/I:N/A:H
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Cisco IOS XE Wireless Controller Software for the Catalyst 9000 Family DHCP
Processing Denial of Service Vulnerability
Priority: High
Advisory ID: cisco-sa-wlc-dhcp-dos-76pCjPxK
First Published: 2022 September 28 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvz97985
CVE Names: CVE-2022-20847
CWEs: CWE-399
Summary
o A vulnerability in the DHCP processing functionality of Cisco IOS XE
Wireless Controller Software for the Catalyst 9000 Family could allow an
unauthenticated, remote attacker to cause a denial of service (DoS)
condition.
This vulnerability is due to the improper processing of DHCP messages. An
attacker could exploit this vulnerability by sending malicious DHCP
messages to an affected device. A successful exploit could allow the
attacker to cause the device to reload, resulting in a DoS condition.
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-wlc-dhcp-dos-76pCjPxK
This advisory is part of the September 2022 release of the Cisco IOS and
IOS XE Software Security Advisory Bundled Publication. For a complete list
of the advisories and links to them, see Cisco Event Response: September
2022 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication.
Affected Products
o Vulnerable Products
This vulnerability affects the following Cisco products if they are running
a vulnerable release of Cisco IOS XE Software and they have the DHCP TLV
caching feature enabled:
Catalyst 9800-CL Wireless Controllers for Cloud
Catalyst 9800 Embedded Wireless Controllers for Catalyst 9300, 9400,
and 9500 Series Switches
Catalyst 9800 Series Wireless Controllers
Embedded Wireless Controllers on Catalyst Access Points
Note: The DHCP TLV caching feature is not enabled by default.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine Whether DHCP TLV Caching is Enabled
To determine whether DHCP TLV caching is enabled, check the settings in the
device web-based management interface using the following steps:
1. Choose Configuration > Tags & Profiles > Policy .
2. Click the appropriate profile name.
3. Choose Access Policies > DHCP TLV Caching .
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:
IOS Software
IOS XR Software
Meraki products
NX-OS Software
Wireless LAN Controller (WLC) AireOS 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 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.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE 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 determine whether a
release is affected by any Cisco Security Advisory. To use the form, follow
these steps:
1. Choose which advisories the tool will search-only this advisory, only
advisories with a Critical or High Security Impact Rating (SIR) , or
all advisories.
2. Enter a release number-for example, 15.9(3)M2 or 17.3.3.
3. Click Check
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.
Related to This Advisory
o Cisco Event Response: September 2022 Semiannual Cisco IOS and IOS XE
Software Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-wlc-dhcp-dos-76pCjPxK
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2022-SEP-28 |
+----------+---------------------------+----------+--------+--------------+
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