---
id: CVE-2020-3571
title: >-
  A vulnerability in the ICMP ingress packet processing of Cisco Firepower
  Threat Defense (FTD) Software for Cisco Firepower 4110 appliances could allow
  an unauthenticated, remote attacker to cause a denial of service (DoS)
  condition on an…
summary: >-
  A vulnerability in the ICMP ingress packet processing of Cisco Firepower
  Threat Defense (FTD) Software for Cisco Firepower 4110 appliances could allow
  an unauthenticated, remote attacker to cause a denial of service (DoS)
  condition on an…
severity: high
cvss: 8.6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'
cwe:
  - CWE-400
  - CWE-20
vendor: cisco
product: secure_firewall_threat_defense
affected:
  - 'secure_firewall_threat_defense >= 6.3.0, < 6.3.0.6'
  - 'secure_firewall_threat_defense >= 6.4.0, < 6.4.0.10'
  - 'secure_firewall_threat_defense >= 6.5.0, < 6.5.0.5'
patched:
  - secure_firewall_threat_defense 6.5.0.5
published: '2020-10-21'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-3571'
references:
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-icmp-dos-hxxcycM
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-icmp-dos-hxxcycM
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.01374
epssPercentile: 0.70791
ingestedAt: '2026-08-18T12:28:06.386Z'
---

## Overview

A vulnerability in the ICMP ingress packet processing of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 4110 appliances could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to incomplete input validation upon receiving ICMP packets. An attacker could exploit this vulnerability by sending a high number of crafted ICMP or ICMPv6 packets to an affected device. A successful exploit could allow the attacker to cause a memory exhaustion condition that may result in an unexpected reload. No manual intervention is needed to recover the device after the reload.

## Affected

- `secure_firewall_threat_defense >= 6.3.0, < 6.3.0.6`
- `secure_firewall_threat_defense >= 6.4.0, < 6.4.0.10`
- `secure_firewall_threat_defense >= 6.5.0, < 6.5.0.5`

## Remediation

Upgrade past the affected range:

- `secure_firewall_threat_defense 6.5.0.5`