---
id: CVE-2020-3533
title: >-
  A vulnerability in the Simple Network Management Protocol (SNMP) input packet
  processor of Cisco Firepower Threat Defense (FTD) Software could allow an
  unauthenticated, remote attacker to cause an affected device to restart
  unexpectedly.…
summary: >-
  A vulnerability in the Simple Network Management Protocol (SNMP) input packet
  processor of Cisco Firepower Threat Defense (FTD) Software could allow an
  unauthenticated, remote attacker to cause an affected device to restart
  unexpectedly.…
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-400
vendor: cisco
product: secure_firewall_threat_defense
affected:
  - 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'
patched:
  - secure_firewall_threat_defense 6.6.1
published: '2020-10-21'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-3533'
references:
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snmp-dos-R8ENPbOs
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snmp-dos-R8ENPbOs
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.01763
epssPercentile: 0.76725
ingestedAt: '2026-08-11T19:48:28.675Z'
---

## Overview

A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to restart unexpectedly. The vulnerability is due to a lack of sufficient memory management protections under heavy SNMP polling loads. An attacker could exploit this vulnerability by sending a high rate of SNMP requests to the SNMP daemon through the management interface on an affected device. A successful exploit could allow the attacker to cause the SNMP daemon process to consume a large amount of system memory over time, which could then lead to an unexpected device restart, causing a denial of service (DoS) condition. This vulnerability affects all versions of SNMP.

## Affected

- `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`

## Remediation

Upgrade past the affected range:

- `secure_firewall_threat_defense 6.6.1`