Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability (CVE-2025-20333)
Severity: critical · Patch status: unknown · Since 2025-09-25 · CVE-2025-20333
Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Software VPN Web Server contain a buffer overflow vulnerability that allows for remote code execution. This vulnerability could be chained with CVE-2025-20362. CISA added CVE-2025-20333 to its Known Exploited Vulnerabilities catalog on Sep 25, 2025, which means attackers are exploiting it in the wild.
What to do
- 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.
- US federal agencies must remediate by Sep 26, 2025 (BOD 22-01); treat that as the outer limit.
Sources
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