Cisco IOS XE Software NETCONF and RESTCONF Authentication Bypass Vulnerability [CVE-2021-1619]

CVE number – CVE-2021-1619

A vulnerability in the authentication, authorization, and accounting (AAA) function of Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass NETCONF or RESTCONF authentication and do either of the following:

  • Install, manipulate, or delete the configuration of an affected device
  • Cause memory corruption that results in a denial of service (DoS) on an affected device

This vulnerability is due to an uninitialized variable. An attacker could exploit this vulnerability by sending a series of NETCONF or RESTCONF requests to an affected device. A successful exploit could allow the attacker to use NETCONF or RESTCONF to install, manipulate, or delete the configuration of a network device or to corrupt memory on the device, resulting a DoS.

Vulnerable Products

This vulnerability affects Cisco IOS XE Software if it is running in autonomous or controller mode and Cisco IOS XE SD-WAN Software. For either to be affected, all of the following must be configured:

  • AAA
  • NETCONF, RESTCONF, or both
  • enable password¬†without¬†enable secret

Workarounds

  • There is a workaround that addresses this vulnerability: Remove the enable password and configure an enable secret. For more information, see Cisco Guide to Harden Cisco IOS Devices.There is also a mitigation that addresses this vulnerability: To limit the attack surface of this vulnerability, ensure that access control lists (ACLs) are in place for NETCONF and RESTCONF to prevent attempted access from untrusted subnets. For more information, see NETCONF and RESTCONF Service-Level ACLs.While this workaround and this mitigation have been deployed and were proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

Fixed Software

  • Cisco has released free software updates that address the vulnerability described in this advisory.

This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-aaa-Yx47ZT8Q

Jason Davies

UK based technology professional, with an interest in computer security and telecoms.

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