---
id: CVE-2020-3373
title: >-
  A vulnerability in the IP fragment-handling implementation of Cisco Adaptive
  Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD)
  Software could allow an unauthenticated, remote attacker to cause a memory
  leak on an…
summary: >-
  A vulnerability in the IP fragment-handling implementation of Cisco Adaptive
  Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD)
  Software could allow an unauthenticated, remote attacker to cause a memory
  leak 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-401
vendor: cisco
product: secure_firewall_threat_defense
affected:
  - secure_firewall_threat_defense = 6.6.0.1
  - adaptive_security_appliance_software = 9.8.4.22
  - adaptive_security_appliance_software = 9.8.4.25
  - adaptive_security_appliance_software = 9.12.4.2
  - adaptive_security_appliance_software = 9.12.4.3
  - adaptive_security_appliance_software = 9.13.1.12
  - adaptive_security_appliance_software = 9.14.1.15
published: '2020-10-21'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-3373'
references:
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-frag-memleak-mCtqdP9n
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-frag-memleak-mCtqdP9n
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.01974
epssPercentile: 0.79599
ingestedAt: '2026-08-11T19:48:28.477Z'
---

## Overview

A vulnerability in the IP fragment-handling implementation of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a memory leak on an affected device. This memory leak could prevent traffic from being processed through the device, resulting in a denial of service (DoS) condition. The vulnerability is due to improper error handling when specific failures occur during IP fragment reassembly. An attacker could exploit this vulnerability by sending crafted, fragmented IP traffic to a targeted device. A successful exploit could allow the attacker to continuously consume memory on the affected device and eventually impact traffic, resulting in a DoS condition. The device could require a manual reboot to recover from the DoS condition. Note: This vulnerability applies to both IP Version 4 (IPv4) and IP Version 6 (IPv6) traffic.

## Affected

- `secure_firewall_threat_defense = 6.6.0.1`
- `adaptive_security_appliance_software = 9.8.4.22`
- `adaptive_security_appliance_software = 9.8.4.25`
- `adaptive_security_appliance_software = 9.12.4.2`
- `adaptive_security_appliance_software = 9.12.4.3`
- `adaptive_security_appliance_software = 9.13.1.12`
- `adaptive_security_appliance_software = 9.14.1.15`

## Remediation

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