CVE-2025-20333 - Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability

Vulnerability Name

Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability

Description

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.

Known To Be Used in Ransomware Campaigns?

Unknown

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.

Additional Notes

CISA Mitigation Instructions: https://www.cisa.gov/news-events/directives/ed-25-03-identify-and-mitigate-potential-compromise-cisco-devices

https://www.cisa.gov/news-events/directives/supplemental-direction-ed-25-03-core-dump-and-hunt-instructions

https://www.cisa.gov/eviction-strategies-tool/create-from-template

https://sec.cloudapps.cisco.com/security/center/resources/asa_ftd_continued_attacks

https://sec.cloudapps.cisco.com/security/center/private/resources/asa_ftd_continued_attacks#Details

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-webvpn-z5xP8EUB

https://nvd.nist.gov/vuln/detail/CVE-2025-20333

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Urgent: Cisco ASA Zero-Day Duo Under Attack; CISA Triggers Emergency Mitigation DirectiveSeptember 26, 2025