A vulnerability in the boot process of Cisco IOS XR Software could allow an authenticated, local attacker to bypass Cisco IOS XR image signature verification and load unverified software on an affected device. To exploit this vulnerability, the attacker must have root-system privileges on the affected device. This vulnerability is due to incomplete validation of files in the boot verification process. An attacker could exploit this vulnerability by manipulating the system configuration options to bypass some of the integrity checks that are performed during the boot process. A successful exploit could allow the attacker to control the boot configuration, which could enable them to bypass the requirement to run Cisco-signed images or alter the security properties of the running system. Note: Because exploitation of this vulnerability could result in the attacker bypassing Cisco image verification, Cisco has raised the Security Impact Rating (SIR) of this advisory from Medium to High.

A vulnerability in the boot process of Cisco IOS XR Software could allow an authenticated, local attacker with high privileges to bypass the Cisco Secure Boot functionality and load unverified software on an affected device. To exploit this successfully, the attacker must have root-system privileges on the affected device. This vulnerability is due to an error in the software build process. An attacker could exploit this vulnerability by manipulating the system’s configuration options to bypass some of the integrity checks that are performed during the booting process. A successful exploit could allow the attacker to control the boot configuration, which could enable them to bypass of the requirement to run Cisco signed images or alter the security properties of the running system.

A vulnerability in the access control list (ACL) processing on Pseudowire interfaces in the ingress direction of Cisco IOS XR Software could allow an unauthenticated, remote attacker to bypass a configured ACL. This vulnerability is due to improper assignment of lookup keys to internal interface contexts. An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to access resources behind the affected device that were supposed to be protected by a configured ACL.

A vulnerability in the SSH client feature of Cisco IOS XR Software for Cisco 8000 Series Routers and Cisco Network Convergence System (NCS) 540 Series and 5700 Series Routers could allow an authenticated, local attacker to elevate privileges on an affected device. This vulnerability is due to insufficient validation of arguments that are included with the SSH client CLI command. An attacker with low-privileged access to an affected device could exploit this vulnerability by issuing a crafted SSH client command to the CLI. A successful exploit could allow the attacker to elevate privileges to root on the affected device.