Actively exploited in the wild
Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability
Cisco - Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense · Listed in the CISA KEV since 2025-09-25. This indicates confirmed attacks in production environments.
Required action: The KEV due date refers to the deadline by which FCEB agencies are expected to review and begin implementing the guidance outlined in Emergency Directive (ED) 25-03 (URL listed below in Notes). Agencies must follow the mitigation steps provided by CISA (URL listed below in Notes) and vendor’s instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
CVE-2025-20333
CriticalCVSS 9.9KEVExploitation Probability (EPSS)
Very high risk99th percentile - higher than 99% of all known CVEs
Summary
A vulnerability in the VPN web server of Cisco Secure Firewall ASA and FTD Software allows an authenticated, remote attacker to execute arbitrary code on the device. The issue is due to improper validation of user-supplied input in HTTP(S) requests. A successful exploit could allow the attacker to execute code as root, potentially leading to full device compromise.
Risk Assessment
Risk of full device compromise by an attacker with valid VPN credentials, potentially leading to network integrity breach and exposure of confidential data.
Recommendation
Apply the patches provided by Cisco immediately and restrict access to the VPN server to trusted users only.
Other vulnerabilities in Cisco Secure Firewall ASA/FTD
See all- CVE-2026-20349HighActively exploited
A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall ASA and FTD Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. The issue is due to insufficient error checking when processing HTTP requests. An attacker could exploit this by sending a crafted HTTP request to the VPN service.
- CVE-2025-20362MediumActively exploited
A vulnerability in the VPN web server of Cisco Secure Firewall ASA and FTD Software allows an unauthenticated, remote attacker to access restricted URL endpoints related to remote access VPN that should be inaccessible without authentication. The issue is due to improper validation of user-supplied input in HTTP(S) requests. A successful exploit could allow access to a restricted URL without authentication.
- CVE-2026-20121Medium
A vulnerability in the access control list (ACL) Object Group Search (OGS) implementation of Cisco Secure Firewall ASA Software and Cisco Secure Firewall Threat Defense (FTD) Software. It is due to a logic error in populating group access control policies (ACPs) with OGS configured. An unauthenticated, remote attacker could send traffic that should be blocked and bypass configured access controls.
- CVE-2026-20120Medium
A vulnerability in the access control list (ACL) Object Group Search (OGS) implementation of Cisco Secure Firewall ASA Software and Cisco Secure Firewall Threat Defense (FTD) Software. It is due to a logic error in populating group access control policies (ACPs) with OGS configured. An unauthenticated, remote attacker could send traffic that should be blocked and bypass configured access controls.
- CVE-2026-20021Medium
A vulnerability in the OSPF protocol of Cisco Secure Firewall ASA Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, adjacent attacker to exhaust memory on an affected device, resulting in a denial of service (DoS) condition. This is due to improper input validation when parsing OSPF packets. Crafted packets can exhaust memory and cause service disruption.
- CVE-2026-20020Medium
A vulnerability in the OSPF protocol of Cisco Secure Firewall ASA Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to cause an affected device to reload unexpectedly, resulting in a DoS condition. If OSPF authentication is enabled, the attacker must know the secret key. This is due to insufficient input validation when processing OSPF update packets. Crafted packets can cause a buffer overflow and device reload.
- CVE-2026-20102Medium
A vulnerability in the SAML 2.0 single sign-on (SSO) feature of Cisco Secure Firewall ASA and FTD Software could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against the SAML feature and access sensitive browser-based information. This is due to insufficient input validation of HTTP parameters. Exploitation requires persuading a user to access a malicious link.
- CVE-2026-20070Medium
A vulnerability in the VPN web services component of Cisco Secure Firewall ASA and FTD Software could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against a browser accessing an affected device. This is due to improper validation of user-supplied input in HTTP requests. Exploitation could allow arbitrary HTML or script execution in the context of the VPN web server.
- CVE-2025-20224Medium
A vulnerability in the IKEv2 module of Cisco Secure Firewall ASA and FTD software could allow an unauthenticated, remote attacker to trigger a memory leak, resulting in a denial of service (DoS) condition. The issue is due to improper parsing of IKEv2 packets.
Original NVD description (English source)
A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP(S) requests. An attacker with valid VPN user credentials could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute arbitrary code as root, possibly resulting in the complete compromise of the affected device.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS