---
id: CVE-2020-3562
title: >-
  A vulnerability in the SSL/TLS inspection of Cisco Firepower Threat Defense
  (FTD) Software for Cisco Firepower 2100 Series firewalls could allow an
  unauthenticated, remote attacker to cause a denial of service (DoS) condition
  on an affec…
summary: >-
  A vulnerability in the SSL/TLS inspection of Cisco Firepower Threat Defense
  (FTD) Software for Cisco Firepower 2100 Series firewalls could allow an
  unauthenticated, remote attacker to cause a denial of service (DoS) condition
  on an affec…
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-119
  - CWE-119
vendor: cisco
product: secure_firewall_threat_defense
affected:
  - secure_firewall_threat_defense = 6.3.0
  - secure_firewall_threat_defense = 6.4.0
  - secure_firewall_threat_defense = 6.5.0
published: '2020-10-21'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-3562'
references:
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-ssl-dcrpt-dos-RYEkX4yy
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-ssl-dcrpt-dos-RYEkX4yy
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.0181
epssPercentile: 0.77697
ingestedAt: '2026-08-11T19:48:28.875Z'
---

## Overview

A vulnerability in the SSL/TLS inspection of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 2100 Series firewalls could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper input validation for certain fields of specific SSL/TLS messages. An attacker could exploit this vulnerability by sending a malformed SSL/TLS message through an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. No manual intervention is needed to recover the device after it has reloaded.

## Affected

- `secure_firewall_threat_defense = 6.3.0`
- `secure_firewall_threat_defense = 6.4.0`
- `secure_firewall_threat_defense = 6.5.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.