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AUSCERT External Security Bulletin Redistribution
Cisco IOS XE ROM Monitor Software for Cisco Industrial
Switches OS Command Injection Vulnerability
25 March 2021
AusCERT Security Bulletin Summary
Product: Cisco IOS XE ROM Monitor Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Execute Arbitrary Code/Commands -- Console/Physical
CVE Names: CVE-2021-1452
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Cisco IOS XE ROM Monitor Software for Cisco Industrial Switches OS Command
Advisory ID: cisco-sa-iosxe-romvar-cmd-inj-N56fYbrw
First Published: 2021 March 24 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvu65039
CVE Names: CVE-2021-1452
o A vulnerability in the ROM Monitor (ROMMON) of Cisco IOS XE Software for
Cisco Catalyst IE3200, IE3300, and IE3400 Rugged Series Switches, Cisco
Catalyst IE3400 Heavy Duty Series Switches, and Cisco Embedded Services
3300 Series Switches could allow an unauthenticated, physical attacker to
execute unsigned code at system boot time.
This vulnerability is due to incorrect validations of specific function
arguments passed to a boot script when specific ROMMON variables are set.
An attacker could exploit this vulnerability by setting malicious values
for a specific ROMMON variable. A successful exploit could allow the
attacker to execute unsigned code and bypass the image verification check
during the secure boot process of an affected device. To exploit this
vulnerability, the attacker would need to have unauthenticated, physical
access to the device or obtain privileged access to the root shell on the
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:
o Vulnerable Products
This vulnerability affects the following Cisco routers if they are running
a Cisco IOS XE ROMMON Software release earlier than Release 7.0:
Catalyst IE3200 Rugged Series Switches
Catalyst IE3300 Rugged Series Switches
Catalyst IE3400 Rugged Series Switches
Catalyst IE3400 Heavy Duty Series Switches
Embedded Services 3300 Series Switches (ESS 3300)
Determine the Cisco IOS XE ROMMON Software Release
To determine which Cisco IOS XE ROMMON Software release is running on a
device, log in to the device and use the show rom-monitor rp active command
in the CLI. The following example shows the output of this command for a
device that is running Cisco IOS XE ROMMON Software Release 7.1.1:
Switch# show rom-monitor rp active
Version 7.1.1 [RELEASE SOFTWARE]
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
IOS XR Software
o There are no workarounds that address this vulnerability.
o Cisco has released free software updates that address the vulnerability
described in this advisory. 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
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.
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
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
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
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
The ROMMON software is a bootstrap program that initializes the hardware
and boots Cisco IOS XE Software when a device is powered on or reloaded.
The ROMMON software is bundled with the Cisco IOS XE binary, which can be
downloaded from the Software Center on Cisco.com.
Customers are advised to upgrade to an appropriate fixed software release
as indicated in the following table:
Affected Cisco Devices First Fixed Cisco IOS XE First Fixed Cisco IOS
ROMMON Software Release XE Software Release
Catalyst IE3200 Rugged 7.0 and later 17.3.1 and later
Catalyst IE3300 Rugged 7.0 and later 17.3.1 and later
Catalyst IE3400 Rugged 7.0 and later 17.3.1 and later
Catalyst IE3400 Heavy 7.0 and later 17.3.1 and later
Duty Series Switches
Embedded Service 3300 7.0 and later 17.3.1 and later
ROMMON code is included as part of a Cisco IOS XE Software binary image,
and it is not available as a standalone binary. Customers looking to
upgrade their ROMMON to a fixed version will need to upgrade the Cisco IOS
XE Software that is running on a device to Release 17.3.1 or later. On
first boot, Cisco IOS XE Software will check the installed ROMMON version
and upgrade it to Release 7.0 if the device is running an older version.
Note: If the device is downgraded to an older Cisco IOS XE Software
release, the ROMMON will be rewritten with a previous ROMMON version, which
may make the device vulnerable.
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.
o This vulnerability was found during internal security testing by X.B. of
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.
| Version | Description | Section | Status | Date |
| 1.0 | Initial public release. | - | Final | 2021-MAR-24 |
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