---
id: CVE-2020-3564
title: >-
  A vulnerability in the FTP inspection engine of Cisco Adaptive Security
  Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software
  could allow an unauthenticated, remote attacker to bypass FTP inspection
summary: >-
  A vulnerability in the FTP inspection engine of Cisco Adaptive Security
  Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software
  could allow an unauthenticated, remote attacker to bypass FTP inspection. The
  vulnerabilit…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'
cwe:
  - CWE-284
  - CWE-436
vendor: cisco
product: adaptive_security_appliance
affected:
  - adaptive_security_appliance < 9.6
  - secure_firewall_threat_defense < 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'
  - 'secure_firewall_threat_defense >= 6.6.0, < 6.6.1'
  - 'adaptive_security_appliance_software >= 9.8.0, < 9.8.4.26'
  - 'adaptive_security_appliance_software >= 9.9.0, < 9.9.2.80'
  - 'adaptive_security_appliance_software >= 9.10.0, < 9.10.1.44'
  - 'adaptive_security_appliance_software >= 9.12.0, < 9.12.4.4'
  - 'adaptive_security_appliance_software >= 9.13.0, < 9.13.1.13'
  - 'adaptive_security_appliance_software >= 9.14.0, < 9.14.1.19'
patched:
  - adaptive_security_appliance 9.6
  - secure_firewall_threat_defense 6.6.1
  - adaptive_security_appliance_software 9.14.1.19
published: '2020-10-21'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-3564'
references:
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ftpbypass-HY3UTxYu
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ftpbypass-HY3UTxYu
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.01329
epssPercentile: 0.69855
ingestedAt: '2026-08-18T12:28:06.227Z'
---

## Overview

A vulnerability in the FTP inspection engine of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass FTP inspection. The vulnerability is due to ineffective flow tracking of FTP traffic. An attacker could exploit this vulnerability by sending crafted FTP traffic through an affected device. A successful exploit could allow the attacker to bypass FTP inspection and successfully complete FTP connections.

## Affected

- `adaptive_security_appliance < 9.6`
- `secure_firewall_threat_defense < 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`
- `secure_firewall_threat_defense >= 6.6.0, < 6.6.1`
- `adaptive_security_appliance_software >= 9.8.0, < 9.8.4.26`
- `adaptive_security_appliance_software >= 9.9.0, < 9.9.2.80`
- `adaptive_security_appliance_software >= 9.10.0, < 9.10.1.44`
- `adaptive_security_appliance_software >= 9.12.0, < 9.12.4.4`
- `adaptive_security_appliance_software >= 9.13.0, < 9.13.1.13`
- `adaptive_security_appliance_software >= 9.14.0, < 9.14.1.19`

## Remediation

Upgrade past the affected range:

- `adaptive_security_appliance 9.6`
- `secure_firewall_threat_defense 6.6.1`
- `adaptive_security_appliance_software 9.14.1.19`