On 2025-09-25, CISA added CVE-2025-20333 (Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense) to its Known Exploited Vulnerabilities (KEV) catalog [2]. The vulnerability is listed in the catalog as "Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability" [2]. CISA requires remediation in accordance with the listed vendor mitigation guidance; see the original text in the body for specific requirements [2].
Backfill: this event became public on Sep 25, 2025 and we added it on Nov 10, 2026. It is not a new event.
CISA Adds Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Vulnerability CVE-2025-20333 to Known Exploited Vulnerabilities Catalog
1 min read
- Disclosed
- Sep 25, 2025
- Published
- Nov 10, 2026
- Last updated
- Nov 8, 2026
- CVSS basis
- Our assessment
- 72%, higher than 99% of CVEs
- Exploitation and patch status
- ExploitedKEV
- Attack vector
- Vulnerability status
- Actor type
- Motivation
On this page
30-second summary
What happened
Who is affected
Industries mainly affected: Government, Cross-industry
What to do nowOur advice
CISA requires remediation in accordance with the listed vendor mitigation guidance; see the original text in the body for specific requirements [2].
Timeline
Technical details
CISA KEV Listing Record
CISA added CVE-2025-20333 (Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense) to the Known Exploited Vulnerabilities () catalog on 2025-09-25 [2].
Original Technical Description
Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Software Web Server contain a buffer overflow vulnerability that allows for . This vulnerability could be chained with CVE-2025-20362. [2]
Official 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 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. [2]
Individual Vulnerability Record
The U.S. National Vulnerability Database (NVD) provides an independent vulnerability record and description for CVE-2025-20333 [1].
References
Official / primary3
- [1]
“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 va”
- [2]
This site aggregates public information and is not security consulting advice. Test remediation steps before applying.