---
id: CVE-2020-3554
title: >-
  A vulnerability in the TCP packet processing of Cisco Adaptive Security
  Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software
  could allow an unauthenticated, remote attacker to cause a denial of service
  (DoS) conditi…
summary: >-
  A vulnerability in the TCP packet processing of Cisco Adaptive Security
  Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software
  could allow an unauthenticated, remote attacker to cause a denial of service
  (DoS) conditi…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-400
  - CWE-400
vendor: cisco
product: adaptive_security_appliance
affected:
  - adaptive_security_appliance < 9.12.4.3
  - secure_firewall_threat_defense <= 6.2.2
  - 'secure_firewall_threat_defense >= 6.3.0, < 6.4.0.10'
  - 'secure_firewall_threat_defense >= 6.5.0, < 6.5.0.5'
  - secure_firewall_threat_defense = 6.6.0
  - 'adaptive_security_appliance_software >= 9.13.0, < 9.13.1.13'
  - 'adaptive_security_appliance_software >= 9.14.0, < 9.14.1.30'
patched:
  - adaptive_security_appliance 9.12.4.3
  - secure_firewall_threat_defense 6.5.0.5
  - adaptive_security_appliance_software 9.14.1.30
published: '2020-10-21'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-3554'
references:
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-dos-QFcNEPfx
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-dos-QFcNEPfx
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.02665
epssPercentile: 0.84998
ingestedAt: '2026-08-11T19:48:28.776Z'
---

## Overview

A vulnerability in the TCP packet processing of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a memory exhaustion condition. An attacker could exploit this vulnerability by sending a high rate of crafted TCP traffic through an affected device. A successful exploit could allow the attacker to exhaust device resources, resulting in a DoS condition for traffic transiting the affected device.

## Affected

- `adaptive_security_appliance < 9.12.4.3`
- `secure_firewall_threat_defense <= 6.2.2`
- `secure_firewall_threat_defense >= 6.3.0, < 6.4.0.10`
- `secure_firewall_threat_defense >= 6.5.0, < 6.5.0.5`
- `secure_firewall_threat_defense = 6.6.0`
- `adaptive_security_appliance_software >= 9.13.0, < 9.13.1.13`
- `adaptive_security_appliance_software >= 9.14.0, < 9.14.1.30`

## Remediation

Upgrade past the affected range:

- `adaptive_security_appliance 9.12.4.3`
- `secure_firewall_threat_defense 6.5.0.5`
- `adaptive_security_appliance_software 9.14.1.30`