A critical vulnerability identified as CVE-2023-20269 has been actively exploited in Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) software, specifically targeting the remote access VPN feature. This vulnerability allows unauthorized remote adversaries to conduct brute-force attacks and potentially establish a clientless SSL VPN session, compromising the security of the affected networks.

Vulnerability Details The CVE-2023-20269 vulnerability arises from inadequate separation of authentication, authorization, and accounting (AAA) functionalities in Cisco’s software. This flaw makes it possible for attackers to perform unauthorized actions without proper credentials if certain conditions on the targeted system are met, such as having SSL VPN or IKEv2 VPN enabled on at least one interface, and using vulnerable versions of Cisco ASA software (version 9.16 and below).

Exploitation and Impact Notably, the Akira and LockBit ransomware groups have leveraged this vulnerability to target organizations. The exploit typically begins with a brute-force attack to ascertain valid usernames and passwords, followed by unauthorized VPN session creation. These attacks primarily focus on systems without multi-factor authentication (MFA), underscoring the necessity of robust authentication measures.

Mitigation and Recommendations Cisco has issued updates to address this vulnerability. However, for systems where updates cannot be immediately applied, Cisco recommends enforcing MFA and applying specific configurations to mitigate potential attacks. These include using Dynamic Access Policies to restrict VPN access and adjusting VPN session settings to prevent unauthorized logins.

Organizational Implications Organizations using Cisco ASA and FTD should urgently upgrade to the patched versions of the software and review their VPN configurations to ensure they include MFA and other recommended security measures. Continuous monitoring for indications of compromise is also advised to detect potential exploitation attempts early.

Further Reading

This analysis underscores the importance of maintaining up-to-date security patches and the implementation of strong, multi-layered security controls to defend against evolving cyber threats.