Known exploited · Cisco
CVE-2024-20353: Cisco ASA and FTD Denial of Service Vulnerability
What it is
Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) contain an infinite loop vulnerability that can lead to remote denial of service condition.
- Vendor
- Cisco
- Product
- Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD)
- Added to KEV
- April 24, 2024
- CISA due date
- May 1, 2024
- Ransomware use
- Unknown
What CISA requires
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Forensic triage
No
What to do now
- Find every instance of Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before May 1, 2024 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.