CVE-2021-1244 in IOS XR
Summary
by MITRE • 02/05/2021
Multiple vulnerabilities in Cisco Network Convergence System (NCS) 540 Series Routers, only when running Cisco IOS XR NCS540L software images, and Cisco IOS XR Software for the Cisco 8000 Series Routers could allow an authenticated, local attacker to execute unsigned code during the boot process on an affected device. For more information about these vulnerabilities, see the Details section of this advisory.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 02/24/2021
The vulnerability identified as CVE-2021-1244 represents a critical security flaw affecting Cisco Network Convergence System 540 Series Routers and Cisco 8000 Series Routers when operating specific IOS XR software versions. This issue stems from insufficient validation mechanisms during the boot process, creating a pathway for authenticated local attackers to execute unauthorized code. The vulnerability specifically impacts devices running Cisco IOS XR NCS540L software images and Cisco IOS XR Software for the Cisco 8000 Series Routers, making it particularly concerning for network infrastructure administrators managing these systems. The attack vector requires local authentication, meaning an attacker must already possess valid credentials to exploit the vulnerability, yet the consequences remain severe due to the privileged execution context during boot operations.
The technical flaw manifests through inadequate code integrity verification mechanisms during the device boot sequence, allowing malicious code to be loaded and executed before the system can properly validate the authenticity of boot components. This vulnerability falls under CWE-1103, which addresses issues related to the improper implementation of code integrity checks during system initialization processes. The flaw enables attackers to bypass normal security controls that would typically prevent unauthorized code execution, effectively creating a backdoor within the device's boot process. The exploitation occurs during the critical early stages of system startup when security mechanisms are not yet fully operational, making traditional runtime protections ineffective against this attack vector. This represents a significant bypass of the principle of least privilege and demonstrates a failure in the system's integrity verification protocols that should prevent unauthorized modifications to critical boot components.
The operational impact of CVE-2021-1244 extends beyond simple code execution, potentially allowing attackers to establish persistent access to network infrastructure and compromise the entire network convergence system. Once exploited, the malicious code could enable attackers to modify routing tables, intercept network traffic, or create unauthorized access points within the network infrastructure. The vulnerability's location within the boot process means that any compromise could persist across device reboots, making detection and remediation particularly challenging. Network administrators face the risk of complete system compromise, potentially affecting hundreds or thousands of network connections depending on the scale of the affected deployment. The vulnerability also undermines the trust model of the network infrastructure, as devices that should maintain secure boot processes become vulnerable to unauthorized modifications.
Mitigation strategies for CVE-2021-1244 should prioritize immediate software updates from Cisco, specifically targeting the patched versions of IOS XR software that address the boot process validation issues. Organizations must implement strict access controls and monitor for unauthorized local access attempts, as the vulnerability requires authentication to exploit. Network segmentation and monitoring of boot processes should be enhanced to detect any anomalous behavior during system startup. The ATT&CK framework categorizes this vulnerability under T1068, which addresses "Exploitation for Privilege Escalation" and T1547, addressing "Boot or Logon Autostart Execution,' highlighting the need for comprehensive defensive measures. Administrators should also consider implementing network monitoring solutions that can detect unusual boot patterns or unauthorized code execution attempts. Regular vulnerability assessments and security audits of network infrastructure should be conducted to identify similar weaknesses in other network devices that may be susceptible to similar boot-time exploitation techniques.