---
id: CVE-2020-3283
title: >-
  A vulnerability in the Secure Sockets Layer (SSL)/Transport Layer Security
  (TLS) handler of Cisco Firepower Threat Defense (FTD) Software when running on
  the Cisco Firepower 1000 Series platform could allow an unauthenticated,
  remote att…
summary: >-
  A vulnerability in the Secure Sockets Layer (SSL)/Transport Layer Security
  (TLS) handler of Cisco Firepower Threat Defense (FTD) Software when running on
  the Cisco Firepower 1000 Series platform could allow an unauthenticated,
  remote att…
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-787
vendor: cisco
product: secure_firewall_threat_defense
affected:
  - 'secure_firewall_threat_defense >= 6.4.0, < 6.4.0.9'
  - asa_5505_firmware = 9.12(2.12)
  - asa_5505_firmware = 9.13(0.33)
  - asa_5510_firmware = 9.12(2.12)
  - asa_5510_firmware = 9.13(0.33)
  - asa_5512-x_firmware = 9.12(2.12)
  - asa_5512-x_firmware = 9.13(0.33)
  - asa_5515-x_firmware = 9.12(2.12)
  - asa_5515-x_firmware = 9.13(0.33)
  - asa_5520_firmware = 9.12(2.12)
  - asa_5520_firmware = 9.13(0.33)
  - asa_5525-x_firmware = 9.12(2.12)
  - asa_5525-x_firmware = 9.13(0.33)
  - asa_5540_firmware = 9.12(2.12)
  - asa_5540_firmware = 9.13(0.33)
  - asa_5545-x_firmware = 9.12(2.12)
  - asa_5545-x_firmware = 9.13(0.33)
  - asa_5550_firmware = 9.12(2.12)
  - asa_5550_firmware = 9.13(0.33)
  - asa_5555-x_firmware = 9.12(2.12)
  - asa_5555-x_firmware = 9.13(0.33)
  - asa_5580_firmware = 9.12(2.12)
  - asa_5580_firmware = 9.13(0.33)
  - asa_5585-x_firmware = 9.12(2.12)
  - asa_5585-x_firmware = 9.13(0.33)
patched:
  - secure_firewall_threat_defense 6.4.0.9
published: '2020-05-06'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-3283'
references:
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tls-dos-4v5nmWtZ
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tls-dos-4v5nmWtZ
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.02005
epssPercentile: 0.79943
ingestedAt: '2026-08-11T19:48:27.782Z'
---

## Overview

A vulnerability in the Secure Sockets Layer (SSL)/Transport Layer Security (TLS) handler of Cisco Firepower Threat Defense (FTD) Software when running on the Cisco Firepower 1000 Series platform could allow an unauthenticated, remote attacker to trigger a denial of service (DoS) condition on an affected device. The vulnerability is due to a communication error between internal functions. An attacker could exploit this vulnerability by sending a crafted SSL/TLS message to an affected device. A successful exploit could allow the attacker to cause a buffer underrun, which leads to a crash. The crash causes the affected device to reload.

## Affected

- `secure_firewall_threat_defense >= 6.4.0, < 6.4.0.9`
- `asa_5505_firmware = 9.12(2.12)`
- `asa_5505_firmware = 9.13(0.33)`
- `asa_5510_firmware = 9.12(2.12)`
- `asa_5510_firmware = 9.13(0.33)`
- `asa_5512-x_firmware = 9.12(2.12)`
- `asa_5512-x_firmware = 9.13(0.33)`
- `asa_5515-x_firmware = 9.12(2.12)`
- `asa_5515-x_firmware = 9.13(0.33)`
- `asa_5520_firmware = 9.12(2.12)`
- `asa_5520_firmware = 9.13(0.33)`
- `asa_5525-x_firmware = 9.12(2.12)`
- `asa_5525-x_firmware = 9.13(0.33)`
- `asa_5540_firmware = 9.12(2.12)`
- `asa_5540_firmware = 9.13(0.33)`
- `asa_5545-x_firmware = 9.12(2.12)`
- `asa_5545-x_firmware = 9.13(0.33)`
- `asa_5550_firmware = 9.12(2.12)`
- `asa_5550_firmware = 9.13(0.33)`
- `asa_5555-x_firmware = 9.12(2.12)`
- `asa_5555-x_firmware = 9.13(0.33)`
- `asa_5580_firmware = 9.12(2.12)`
- `asa_5580_firmware = 9.13(0.33)`
- `asa_5585-x_firmware = 9.12(2.12)`
- `asa_5585-x_firmware = 9.13(0.33)`

## Remediation

Upgrade past the affected range:

- `secure_firewall_threat_defense 6.4.0.9`