Summary

• Multiple vulnerabilities in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to gain access to the underlying root shell of an affected device and execute arbitrary commands with root privileges.

  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-iosxr-cmd-inj-wbZKvPxc

  This advisory is part of the September 2021 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2021 Cisco IOS XR Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  At the time of publication, CVE-2021-34721 affected Cisco IOS XR Software releases earlier than Release 7.3.2 if the xml agent feature was configured.

  At the time of publication, CVE-2021-34722 affected Cisco IOS XR Software releases 7.1.1 through 7.3.1.

  See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  Determine the Device Configuration

  To determine if the xml agent is enabled, use the following command:

  RP/0/RP0/CPU0: router# show running-config | include xml agent
  xml agent tty

  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:

  • IOS Software
  • IOS XE Software
  • NX-OS Software

Details

• The vulnerabilities are not dependent on one another. Exploitation of one of the vulnerabilities is not required to exploit another vulnerability. In addition, a software release that is affected by one of the vulnerabilities may not be affected by the other vulnerabilities.

  Details about the vulnerabilities are as follows:

  CVE-2021-34721: Cisco IOS XR Software Command Injection Vulnerability

  A vulnerability in the XML configuration manager of Cisco IOS XR Software could allow an authenticated, local attacker to inject arbitrary commands that are executed with root privileges on the underlying Linux operating system (OS) of an affected device.

  This vulnerability is due to insufficient input validation of commands that are supplied by a user. An attacker could exploit this vulnerability by authenticating to a device and submitting crafted input to affected commands. A successful exploit could allow an attacker to gain access to the underlying root shell of the affected device and execute arbitrary commands as root.

  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

  Bug ID(s): CSCvx48002
  CVE ID: CVE-2021-34721
  Security Impact Rating (SIR): Medium
  CVSS Base Score: 6.7
  CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

  CVE-2021-34722: Cisco IOS XR Software Command Injection Vulnerability

  A vulnerability in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to gain access to the root shell of an affected device and execute arbitrary commands with root privileges.

  The vulnerability exists because the affected software improperly sanitizes command arguments. An attacker could exploit this vulnerability by authenticating to the device and using CLI commands that contain crafted arguments. A successful exploit could allow the attacker to gain access to the underlying root shell of the affected device and execute arbitrary commands with root privileges.

  Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

  Bug ID(s): CSCvx48001
  CVE ID: CVE-2021-34722
  Security Impact Rating (SIR): Medium
  CVSS Base Score: 6.7
  CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Workarounds

• There are no workarounds that address these vulnerabilities.

Fixed Software

• 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.

  Fixed Releases

  At the time of publication, the following Cisco IOS XR Software releases contained the fix for these vulnerabilities:

  • 7.3.2 and later
  • 7.4.1 and later

  Cisco has released the following SMUs to address these vulnerabilities. Customers who require SMUs for platforms or releases that are not listed are advised to contact their support organization.

  The SMUs in the following table address Cisco Bug ID CSCvx48002.

  Cisco IOS XR Software Release	Platform	SMU Name
  6.6.3	IOSXRWBD	iosxrwbd-6.6.3.CSCvx48002
  7.0.1	NCS5500	ncs5500-7.0.1.CSCvx48002
  7.2.1	ASR9K-X64	asr9k-x64-7.1.3.CSCvw95930

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.

Source

• These vulnerabilities were found during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-cmd-inj-wbZKvPxc

Revision History

• Version	Description	Section	Status	Date
  1.1	Added SMU table.	Fixed Software	Final	2021-SEP-17
  1.0	Initial public release.	-	Final	2021-SEP-08

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