Headline
CVE-2023-20082: Cisco Security Advisory: Cisco IOS XE Software for Cisco Catalyst 9300 Series Switches Secure Boot Bypass Vulnerability
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 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.htmlAdditionally, 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.
- 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.