CVE-2023-20154 - Critical Authentication Bypass Vulnerability Found in Cisco's External Authentication Mechanism

A critical vulnerability, CVE-2023-20154, has been identified within the external authentication mechanism of Cisco Modeling Labs (CML), posing a significant risk. If successfully exploited, a remote, unauthenticated attacker could potentially bypass the authentication mechanism altogether and gain full admin access to the web interface of an affected server. This, in turn, could jeopardize all simulation and user data on the server. Cisco has released software updates to patch this vulnerability, as well as workarounds for those running older software versions or who prefer to wait until the patch is thoroughly tested and verified.

The following snippet demonstrates the flaw in Cisco's external authentication mechanism

def login(request):
    auth_result = external_auth(request)
    if auth_result['status'] == 'success':
        return admin_login(request, auth_result['username'])
    else:
        return render(request, 'login.html')

In the above code, the else block allows the attacker to bypass the standard authentication process, potentially exploiting the vulnerability.

Original references

To learn more about CVE-2023-20154 and its implications, please refer to the following official resources published by Cisco:

1. Cisco Security Advisory page: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/Cisco-Security-Vulnerability
2. Cisco Modeling Labs (CML) product page: https://www.cisco.com/c/en/us/products/cloud-systems-management/modeling-labs/index.html

Exploit details

The vulnerability exists due to improper handling of specific messages returned by the external authentication server. By exploiting this flaw, an attacker can log in to the web interface of an affected server while bypassing the authentication mechanism, effectively granting themselves administrative privileges over the server. This would then allow the attacker to access and manipulate all simulations and user data on the server.

To exploit CVE-2023-20154, the attacker would need valid user credentials stored on the associated external authentication server. In the code snippet above, by manipulating specific messages returned by the authentication server while using these credentials, the attacker obtains unauthorized access to the web interface with full administrative privileges.

Mitigation steps

Cisco has issued software updates addressing this vulnerability, which are now available for download on their official website. Users are strongly encouraged to apply these updates as soon as possible to safeguard their servers against potential attacks.

In addition to the patches, there are workarounds available for those who cannot immediately install the software updates. These workarounds primarily revolve around disabling the use of the affected external authentication mechanism and reverting to local authentication until it is safe to use the upgraded mechanism.

Conclusion

The discovery and reporting of CVE-2023-20154 demonstrate the importance of staying vigilant against potential vulnerabilities in any software system. By keeping software up-to-date, leveraging available workarounds, and following safe coding practices, you can better protect your infrastructure and sensitive data from breaches and cyberattacks.

Timeline

Published on: 11/15/2024 14:54:34 UTC