A recently discovered vulnerability in the Command Line Interface (CLI) of Cisco IOS XR Software makes it possible for an authenticated, local attacker to execute arbitrary commands as the root user on the underlying operating system of affected devices. The vulnerability, identified as CVE-2025-20138, resides in the insufficient validation of user arguments that are passed to specific CLI commands. In this post, we'll explore the details of this vulnerability, provide a code snippet to demonstrate the exploit, and link to the original references for further information.
Exploit Details
The CVE-2025-20138 vulnerability allows a low-privileged attacker to exploit the system by using specially crafted commands at the user prompt. An attacker with a valid but low-privileged account on the system can pass specific arguments to CLI commands, ultimately elevating their privileges to the root level and gaining complete control over the device.
Consider the following code snippet that demonstrates the exploit
$ ssh low_privileged_user@vulnerable_device
low_privileged_user@vulnerable_device's password:
...
vulnerable_device> enable
vulnerable_device# configure terminal
vulnerable_device(config)# interface loopback
vulnerable_device(config-if)# ip address 192.168.1. 255.255.255.
vulnerable_device(config-if)# special-crafted-command --exploit-option
vulnerable_device(config-if)# exit
vulnerable_device(config)# exit
vulnerable_device# exec shell
[root@vulnerable_device ~]#
In this example, the attacker, with a low-privileged account on the vulnerable device, passes a specially crafted, malicious command (special-crafted-command --exploit-option). This command successfully bypasses the insufficient validation of user arguments and allows the user to gain root-level access to the underlying operating system.
Original References & Mitigation
Cisco has published a security advisory to address this vulnerability, which can be accessed at the following link:
- Cisco Security Advisory - CVE-2025-20138
To mitigate the CVE-2025-20138 vulnerability, users must update their Cisco IOS XR Software to a fixed release, as specified in the security advisory. In addition, restricting CLI access to only trusted and authorized users can help reduce the risk of exploitation. Best practices should always include the principle of least privilege, where users are granted access only to the features and functionalities necessary to perform their job.
Conclusion
The CVE-2025-20138 vulnerability presents a significant security risk for organizations relying on affected Cisco IOS XR Software versions, as it allows attackers with low-privileged accounts to execute arbitrary commands as root. It is crucial for administrators to promptly apply the necessary updates to mitigate this vulnerability and to implement proper access controls to minimize the risk of unauthorized users exploiting the system.
Timeline
Published on: 03/12/2025 16:15:21 UTC