Cisco Duo Policy Allowing Outdated Flash Usage

This threat brief focuses on the potential weakening of security controls within Cisco Duo environments. Specifically, it addresses the scenario where a Duo administrator modifies or creates a policy to permit the use of outdated Adobe Flash components. This is identified through Duo activity logs by detecting policy changes with the attribute "flash_remediation=no remediation". The scope of this threat involves any organization using Cisco Duo for multi-factor authentication and where Flash-based applications or services are still in use, despite Flash reaching end-of-life. This policy change can significantly broaden the attack surface, as outdated Flash versions are riddled with known security vulnerabilities. Attackers may exploit these weaknesses to bypass authentication controls, potentially leading to unauthorized access, malware deployment, or privilege escalation. Defenders should be aware of this as it can undermine the overall security posture of the organization and lead to compliance violations.

Attack Chain

1. An attacker gains initial access to a Cisco Duo administrator's account through compromised credentials or social engineering.
2. The attacker logs into the Cisco Duo Admin Panel with the compromised administrator account.
3. The attacker navigates to the "Policies" section of the Duo Admin Panel.
4. The attacker modifies an existing policy or creates a new policy to allow the use of outdated Flash components by setting "flash_remediation=no remediation".
5. The policy change is saved, and the updated configuration is applied to the targeted users or applications.
6. A user with an outdated Flash version attempts to authenticate through Duo.
7. Due to the modified policy, the user is granted access despite the outdated Flash version.
8. The attacker leverages the Flash vulnerability on the user's system to execute malicious code, potentially leading to data theft or system compromise.

Impact

A successful attack leveraging a policy allowing outdated Flash in Cisco Duo can lead to several negative consequences. Attackers can bypass multi-factor authentication, gaining unauthorized access to sensitive systems and data. Depending on the targeted systems, this could result in data breaches, financial losses, and reputational damage. The impact is especially significant for organizations in regulated industries that require strict adherence to security compliance standards. The number of potential victims depends on the scope of the vulnerable policy and the number of users still relying on outdated Flash components.

Recommendation

• Deploy the Sigma rule Cisco Duo Policy Allowing Outdated Flash to detect instances where Duo administrators create or update policies to allow outdated Flash versions. This will provide real-time alerting of potentially malicious policy changes (rule).
• Review all existing Cisco Duo policies and ensure that Flash remediation is enabled ("flash_remediation=remediation") to prevent the exploitation of Flash vulnerabilities.
• Enforce a policy of disabling or removing Flash from all endpoints where it is not absolutely necessary.
• Investigate any alerts generated by the Sigma rule to determine the intent behind the policy change and whether the administrator account was compromised.
• Monitor Cisco Duo activity logs using the cisco_duo_administrator data source for suspicious activity patterns, such as unusual login times or policy changes made outside of normal business hours.
• Utilize the Cisco Security Cloud App (referenced in the provided URL) to ingest Cisco Duo activity logs into your SIEM for centralized monitoring and analysis.