Cisco Security Advisory
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CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X
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Multiple vulnerabilities that affect Cisco Catalyst Digital Building Series Switches and Cisco Catalyst Micro Switches could allow an attacker to execute persistent code at boot time or to permanently prevent the device from booting, resulting in a permanent denial of service (DoS) condition.
For more information about these vulnerabilities, see the Details section of this advisory.
Cisco has released software updates that address these vulnerabilities. There are no workarounds that address these vulnerabilities.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cdb-cmicr-dos-KJjFtNb
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Vulnerable Products
These vulnerabilities affect the following Cisco products if they are running a release of Cisco IOS Software that contains Cisco Boot Loader Version 15.2(7r)E2:
- Catalyst Digital Building Series Switches with product identifiers (PIDs) CDB-8P and CDB-8U (CVE-2022-20661 and CVE-2022-20731)
- Catalyst Micro Switches with PIDs CMICR-4PS and CMICR-4PC (CVE-2022-20661)
For information about which Cisco IOS Software releases contain the fixed boot loader, see the Fixed Software section of this advisory.
Determine the Boot Loader Version
To determine the boot loader version, use the show version | include BOOTLDR command on the device CLI.
Cisco Catalyst Digital Building Series Switches
The following example shows the output of the show version | include BOOTLDR command on a Cisco Catalyst Digital Building Series Switch that is running Cisco Boot Loader Version 15.2(7r)E2:
cdb> show version | include BOOTLDR
BOOTLDR: CDB Boot Loader (CDB-HBOOT-M) Version 15.2(7r)E2, RELEASE SOFTWARE (fc2)Any other output indicates that the device is not affected by these vulnerabilities.
Cisco Catalyst Micro Switches
The following example shows the output of the show version | include BOOTLDR command on a Cisco Catalyst Micro Switch that is running Cisco Boot Loader Version 15.2(7r)E2:
cmicr> show version | include BOOTLDR
BOOTLDR: CMICR Boot Loader (CMICR-HBOOT-M) Version 15.2(7r)E2, RELEASE SOFTWARE (fc2)Any other output indicates that the device is not affected by these vulnerabilities.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by these vulnerabilities.
Cisco has confirmed that these vulnerabilities do not affect the following Cisco products:
- Catalyst Micro Switch with PID CMICR-4PT
- IOS XE Software
- IOS XR Software
- Meraki products
- NX-OS Software
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The vulnerabilities are not dependent on one another. Exploitation of one of the vulnerabilities is not required to exploit the other vulnerability. In addition, a software release that is affected by one of the vulnerabilities may not be affected by the other vulnerability.
Details about the vulnerabilities are as follows:
CVE-2022-20731: Cisco Catalyst Digital Building Series Switches Boot Loader Arbitrary Code Execution Vulnerability
A vulnerability in the boot loader of Cisco Catalyst Digital Building Series Switches could allow an authenticated, local attacker with level 15 privileges or an unauthenticated attacker with physical access to an affected device to execute persistent code at boot time and break the chain of trust.
This vulnerability exists because Secure Boot is not properly enabled. An attacker could exploit this vulnerability by loading unsigned code. A successful exploit could allow the attacker to execute persistent code on the underlying operating system.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
Bug ID(s): CSCvz34674
CVE ID: CVE-2022-20731
Security Impact Rating (SIR): High
CVSS Base Score: 6.8
CVSS Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVE-2022-20661: Cisco Catalyst Digital Building Series Switches and Cisco Catalyst Micro Switches Permanent Denial of Service Vulnerability
A vulnerability in the boot loader of Cisco Catalyst Digital Building Series Switches and Cisco Catalyst Micro Switches could allow an unauthenticated attacker with physical access to an affected device to permanently prevent the device from booting, resulting in a permanent denial of service (DoS) condition.
This vulnerability exists because the affected devices have an internal Cisco development boot loader that includes capabilities beyond those present in a normal boot loader. An attacker with physical access to an affected device could exploit this vulnerability by causing the device to reboot, breaking into the ROM monitor (ROMMON) during the boot cycle, and then executing specific commands at the ROMMON prompt. A successful exploit could allow the attacker to irrecoverably corrupt the boot ROM in such a way that the device will be unable to boot correctly during the next boot cycle. The device will continue to operate normally until it is reloaded or power-cycled.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
Bug ID(s): CSCvz02634, CSCvz30892, CSCvz42624, CSCvz57636
CVE ID: CVE-2022-20661
Security Impact Rating (SIR): Medium
CVSS Base Score: 4.6
CVSS Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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There are no workarounds that address these vulnerabilities.
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Cisco has released free software updates that address the vulnerabilities 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
In the following table(s), the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerabilities described in this advisory and the first release that includes the fix for these vulnerabilities. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Catalyst Digital Building Series Switches (CVE-2022-20661 and CVE-2022-20713)
Cisco IOS Software Release First Fixed Release 15.2(5)EX Migrate to a fixed release. 15.2(7)E and earlier 15.2(7)E5 Catalyst Micro Switches (CVE-2022-20661)
Cisco IOS Software Release First Fixed Release 15.2(7)E and earlier 15.2(7)E5 15.2(8)E 15.2(8)E1 The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
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The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.
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These vulnerabilities were found during internal security testing.
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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.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2022-APR-13
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