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AUSCERT External Security Bulletin Redistribution
ESB-2023.1727.2
Cisco IOS XE Software for Cisco Catalyst 9300 Series
Switches Secure Boot Bypass Vulnerability
1 June 2023
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XE Software for Cisco Catalyst 9300 Series
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2023-20082
Original Bulletin:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-c9300-spi-ace-yejYgnNQ
Comment: CVSS (Max): 6.1 CVE-2023-20082 (CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Revision History: June 1 2023: Vendor Clarified upgrade requirements
March 23 2023: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS XE Software for Cisco Catalyst 9300 Series Switches Secure Boot
Bypass Vulnerability
Priority: High
Advisory ID: cisco-sa-c9300-spi-ace-yejYgnNQ
First Published: 2023 March 22 16:00 GMT
Last Updated: 2023 May 11 15:34 GMT
Version 1.1: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCwa61120
CVE Names: CVE-2023-20082
Summary
o A vulnerability in Cisco IOS XE Software for Cisco Catalyst 9300 Series
Switches could allow an authenticated, local attacker with level-15
privileges or an unauthenticated attacker with physical access to the
device to execute persistent code at boot time and break the chain of
trust.
This vulnerability is due to errors that occur when retrieving the public
release key that is used for image signature verification. An attacker
could exploit this vulnerability by modifying specific variables in the
Serial Peripheral Interface (SPI) flash memory of an affected device. A
successful exploit could allow the attacker to execute persistent code on
the underlying operating system.
Note: In Cisco IOS XE Software releases 16.11.1 and later, the complexity
of an attack using this vulnerability is high. However, an attacker with
level-15 privileges could easily downgrade the Cisco IOS XE Software on a
device to a release that would lower the attack complexity.
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-c9300-spi-ace-yejYgnNQ
Affected Products
o Vulnerable Products
This vulnerability affects Cisco Catalyst 9300 Series Switches if they are
running Cisco IOS XE Software with a release of Cisco IOS XE ROM Monitor
(ROMMON) that is earlier than Release 17.3.7r, Release 17.6.5r, or Release
17.8.1r.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine the Cisco IOS XE ROMMON Release
To determine the Cisco IOS XE ROMMON release that is running on the device,
use the show version | include BOOTLDR command on the device CLI. The
following example shows the output of the show version | include BOOTLDR
command on a device that is running Cisco IOS XE ROMMON Release 17.6.1r:
switch#show version | include BOOTLDR
BOOTLDR: System Bootstrap, Version 17.6.1r[FC2], RELEASE SOFTWARE (P)
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:
Catalyst 9200 Series Switches
Catalyst 9400 Series and 9400X Switches
Catalyst 9500 Series and 9500X Switches
Catalyst 9600 Series and 9600X Switches
IOS Software
IOS XR Software
Meraki products
NX-OS 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.
Fixed Releases
Customers are advised to upgrade to an appropriate fixed software release
as indicated in the following table(s):
Cisco IOS XE Software Release First Fixed Release
16.11 and earlier Migrate to a fixed release.
16.12 Migrate to a fixed release.
17.1 Migrate to a fixed release.
17.2 Migrate to a fixed release.
17.3 17.3.7 (includes ROMMON 17.3.7r)
17.4 Migrate to a fixed release.
17.5 Migrate to a fixed release.
17.6 17.6.5 (includes ROMMON 17.6.5r)
17.7 Migrate to a fixed release.
17.8 Not vulnerable (includes ROMMON 17.8.1r).
17.9 Not vulnerable (includes ROMMON 17.9.1r).
17.10 Not vulnerable (includes ROMMON 17.10.1r).
Notes:
ROMMON can only be updated by upgrading to a Cisco IOS XE Software
release that includes the updated ROMMON release.
Upgrade to a Cisco IOS XE Software release that includes an updated
ROMMON release that has a release number that is higher than the
release number of the ROMMON release currently running on the device.
For example, if you are currently running Cisco IOS XE Software Release
17.3.6 with ROMMON Release 17.6.1r, you need to upgrade to Cisco IOS XE
Software Release 17.6.5 (which includes ROMMON Release 17.6.5r) or
later or Cisco IOS XE Software Release 17.8.1 (which includes ROMMON
Release 17.8.1r) or later. Upgrading to Cisco IOS XE Software Release
17.3.7 will not install the updated ROMMON Release 17.3.7r in this
scenario, as moving from ROMMON Release 17.6.1r to Release 17.3.7r
would be considered a ROMMON downgrade, which is not allowed.
For a complete fix, customers should also upgrade ROMMON in the golden
SPI flash device by using the upgrade rom-monitor capsule golden switch
command. This update should be done after the automatic ROMMON upgrade
in the primary SPI flash device. See the ROMMON Upgrades section of the
Release Notes for Cisco Catalyst 9300 Series Switches for further
information on ROMMON upgrades.
Following the upgrade to a fixed ROMMON release, including the ROMMON
upgrade in the golden SPI flash device, customers could downgrade to an
earlier release of Cisco IOS XE Software but retain the fix for this
vulnerability.
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 This vulnerability was found during internal security testing by X.B. of
the Cisco Advanced Security Initiatives Group (ASIG).
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
URL
o https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-c9300-spi-ace-yejYgnNQ
Revision History
o +---------+--------------------------+-------------+--------+-------------+
| Version | Description | Section | Status | Date |
+---------+--------------------------+-------------+--------+-------------+
| 1.1 | Clarified upgrade | Fixed | Final | 2023-MAY-11 |
| | requirements. | Releases | | |
+---------+--------------------------+-------------+--------+-------------+
| 1.0 | Initial public release. | - | Final | 2023-MAR-22 |
+---------+--------------------------+-------------+--------+-------------+
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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