Cisco · Adaptive Security Appliance and Firepower Threat Defense
CVE-2023-20269
Cisco Adaptive Security Appliance and Firepower Threat Defense Unauthorized Access Vulnerability
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.
CISA: Cisco Adaptive Security Appliance and Firepower Threat Defense contain an unauthorized access vulnerability that could allow an unauthenticated, remote attacker to conduct a brute force attack in an attempt to identify valid username and password combinations or establish a clientless SSL VPN session with an unauthorized user.
What to do
Apply mitigations per vendor instructions for group-lock and vpn-simultaneous-logins or discontinue use of the product for unsupported devices.
Deadline for US federal agencies: October 4, 2023
More exploited flaws from Cisco
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Oct 14, 2026 | Relative Path Traversal | Secure Email Gateway | Critical 9.8 | 2.2% |
| Sep 30, 2026 | Hex Encoding | Catalyst SD-WAN Manager | Critical 9.8 | 39% |
| Sep 16, 2026 | Incorrect Use of Privileged APIs | Identity Services Engine | Critical 10.0 | 76% |
| Sep 14, 2026 | SQL Injection | Secure Email Gateway | Critical 9.8 | 30% |
| Sep 9, 2026 | Firewall Management Center Authentication Bypass Using an Alternate Path or Channel | Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management | Critical 10.0 | 88% |
| Aug 11, 2026 | Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection | Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) | High 8.6 | 1.0% |
| Jul 29, 2026 | Secure Firewall Management Center Use of Hard-coded Password | Secure Firewall Management Center (FMC) | Medium 5.3 | 35% |
| Jul 13, 2026 | Cross-Site Request Forgery | IOS | High 8.1 | 34% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.