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.
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.