CVE-2025-20333
Published 2025-09-25 · Updated 2026-10-18 · Source psirt@cisco.com
Summary
CVE-2025-20333 is a critical-severity (CVSS 9.9) vulnerability in Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense. CISA added it to the Known Exploited Vulnerabilities catalog on September 25, 2025, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by September 26, 2025. CISA does not currently list it as used in ransomware campaigns. Cisco has 102 vulnerabilities in the KEV catalog, 7 of them linked to ransomware.
All 102 known-exploited Cisco vulnerabilities →Description
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.
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CISA Known-Exploited Vulnerability
Product: Cisco — Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense
Name: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability
Date added: 2025-09-25 · Due: 2025-09-26
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.