CVE-2023-20269: Adaptive Security Appliance and Firepower Threat Defense Unauthorized Access

What it is

A vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct a brute force attack in an attempt to identify valid username and password combinations or an authenticated, remote attacker to establish a clientless SSL VPN session with an unauthorized user. This vulnerability is due to improper separation of authentication, authorization, and accounting (AAA) between the remote access VPN feature and the HTTPS management and site-to-site VPN features. An attacker could exploit this vulnerability by specifying a default connection profile/tunnel group while conducting a brute force attack or while establishing a clientless SSL VPN session using valid credentials. A successful exploit could allow the attacker to achieve one or both of the following: Identify valid credentials that could then be used to establish an unauthorized remote access VPN session. Establish a clientless SSL VPN session (only when running Cisco ASA Software Release 9.16 or earlier). Notes: Establishing a client-based remote access VPN tunnel is not possible as these default connection profiles/tunnel groups do not and cannot have an IP address pool configured. This vulnerability does not allow an attacker to bypass authentication. To successfully establish a remote access VPN session, valid credentials are required, including a valid second factor if multi-factor authentication (MFA) is configured. Cisco will release software updates that address this vulnerability. There are workarounds that address this vulnerability.

Exploitation

In August 2023, the Cisco Product Security Incident Response Team (PSIRT) became aware of attempted exploitation of this vulnerability in the wild. Cisco strongly recommends that customers upgrade to a fixed software release to remediate this vulnerability once available and apply one of the suggested workarounds in the meantime.

For information on observed attempted exploitation of this vulnerability, see the Cisco blog post on Akira Ransomware Targeting VPNs without Multi-Factor Authentication ["https://blogs.cisco.com/security/akira-ransomware-targeting-vpns-without-multi-factor-authentication"]. As explained in this blog post, organizations can significantly reduce the risk of unauthorized access, including a potential ransomware infection, by enabling MFA in VPN implementations.

CISA lists this CVE as exploited in the wild since 13 Sept 2023, including in ransomware campaigns.