Cisco ASA and FTD Denial of Service Vulnerability
Cisco — Cisco Adaptive Security Appliance (ASA) Software
A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to incomplete error checking when parsing an HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to a targeted web server on a device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.
8.6
70.7%
Vector breakdown
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- Published
- Apr 24, 2024
- Modified
- Oct 21, 2025
- Added to KEV
- Apr 24, 2024
- Federal patch due
- May 1, 2024
CISA required action
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Weakness classification
Proof-of-concept & exploitation references
Weaponization
Public repositories whose name or description references CVE-2024-20353, found via a live GitHub search at request time. These are community-sourced signals, not a verified working exploit - cross-check each one before relying on it, and treat higher star counts and recent activity as (weak) corroboration, not proof.
No public GitHub repositories referencing CVE-2024-20353 were found at last check. Absence here is not proof no exploit exists - see the references below for vendor advisories and write-ups.
References
Frequently asked questions
What is CVE-2024-20353?
A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to incomplete error checking when parsing an HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to a targeted web server on a device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.
How severe is CVE-2024-20353?
CVE-2024-20353 has a CVSS base score of 8.6 out of 10 (CVSS 3.1).
Is CVE-2024-20353 actively exploited in the wild?
Yes. CVE-2024-20353 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added Apr 24, 2024, meaning CISA has confirmed evidence of active exploitation.
What is the EPSS score for CVE-2024-20353?
70.7% - meaning FIRST.org's EPSS model estimates a 70.7% probability this vulnerability will be exploited in the wild within 30 days (99% percentile among all scored CVEs).
What type of vulnerability is CVE-2024-20353?
CVE-2024-20353 is classified under CWE-835 (Loop with Unreachable Exit Condition ('Infinite Loop')).
Cross-checked against
Impactr finds and proves whether CVE-2024-20353 - or flaws like it - are actually reachable in your own web apps and APIs, with a reproducible exploit as evidence.
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