CVE-2026-20040 in IOS XR
Summary
by MITRE • 03/11/2026
A vulnerability in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to execute arbitrary commands as root on the underlying operating system of an affected device.
This vulnerability is due to insufficient validation of user arguments that are passed to specific CLI commands. An attacker with a low-privileged account could exploit this vulnerability by using crafted commands at the prompt. A successful exploit could allow the attacker to elevate privileges to root and execute arbitrary commands on the underlying operating system.
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Analysis
by VulDB Data Team • 03/14/2026
This vulnerability resides within the command line interface of Cisco IOS XR Software, representing a critical privilege escalation flaw that undermines the security posture of network infrastructure devices. The vulnerability stems from inadequate input validation mechanisms within the CLI processing framework, creating a pathway for authenticated local attackers to bypass normal access controls and gain root-level system privileges. The flaw specifically affects how the system handles user arguments passed to certain CLI commands, allowing malicious input to be interpreted and executed with elevated privileges. This represents a fundamental failure in the software's security architecture where user-supplied data is not properly sanitized before being processed by the underlying operating system components. The vulnerability impacts devices running Cisco IOS XR Software where the affected CLI commands are available, potentially affecting a wide range of network equipment including routers and switches that utilize this operating system.
The technical exploitation of this vulnerability requires an attacker to possess a valid low-privileged account on the target system, which significantly reduces the barrier to entry for potential exploitation. Once authenticated, the attacker can craft specific command sequences that exploit the insufficient argument validation, allowing the system to execute arbitrary code with root privileges. This type of vulnerability falls under the CWE category of Command Injection, specifically CWE-77, which describes situations where commands are constructed using untrusted input without proper validation or sanitization. The attack vector is local and authenticated, making it particularly concerning for environments where multiple users have access to the device console or where privilege escalation is not properly controlled. The underlying operating system architecture of Cisco IOS XR provides the execution environment where these malicious commands are processed, creating a direct pathway from the vulnerable CLI interface to system-level privilege escalation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete control over the affected device's underlying operating system. With root privileges, an attacker can modify system configurations, install malicious software, access sensitive data, and potentially use the compromised device as a pivot point for attacks on other network segments. The vulnerability affects the integrity and confidentiality of the entire network infrastructure, as it allows attackers to manipulate routing tables, modify network policies, and potentially establish persistent access. This type of attack aligns with the ATT&CK framework's privilege escalation techniques, specifically targeting the T1068 - Exploitation for Privilege Escalation tactic, where attackers leverage software vulnerabilities to gain higher-level system access. The impact is particularly severe in enterprise environments where network devices are critical infrastructure components, as a successful exploitation could lead to complete network compromise and data exfiltration.
Mitigation strategies for this vulnerability should focus on immediate patch deployment from Cisco, which would address the underlying input validation issues in the CLI processing components. Network administrators should implement the principle of least privilege by limiting access to device console interfaces and ensuring that only authorized personnel have low-privileged accounts that could potentially be exploited. Additional protective measures include monitoring CLI command usage patterns for suspicious activity, implementing strong authentication controls, and regularly reviewing system logs for evidence of unauthorized access attempts. Organizations should also consider network segmentation and access controls to limit the potential damage if a device becomes compromised. The vulnerability demonstrates the importance of proper input validation and privilege separation in network operating systems, highlighting the need for continuous security assessment of critical infrastructure components. Regular security audits and vulnerability assessments should be conducted to identify similar issues in other system components, as this vulnerability represents a broader class of security flaws that can compromise system integrity and availability.