---
id: CVE-2018-0231
title: >-
  A vulnerability in the Transport Layer Security (TLS) library of Cisco
  Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense
  (FTD) Software could allow an unauthenticated, remote attacker to trigger a
  reload of th…
summary: >-
  A vulnerability in the Transport Layer Security (TLS) library of Cisco
  Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense
  (FTD) Software could allow an unauthenticated, remote attacker to trigger a
  reload of th…
severity: high
cvss: 8.6
cvssVector: 'CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'
cwe:
  - CWE-20
  - CWE-787
vendor: cisco
product: secure_firewall_threat_defense
affected:
  - adaptive_security_appliance_software = 9.8(1)
  - adaptive_security_appliance_software = 98.1(1.154)
  - 'secure_firewall_threat_defense >= 6.0, < 6.1.0.6'
  - 'secure_firewall_threat_defense >= 6.2.1, < 6.2.2.1'
patched:
  - secure_firewall_threat_defense 6.2.2.1
published: '2018-04-19'
updated: '2026-08-11'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2018-0231'
references:
  - url: 'http://www.securitytracker.com/id/1040725'
    label: psirt@cisco.com
  - url: 'https://ics-cert.us-cert.gov/advisories/ICSA-18-184-01'
    label: psirt@cisco.com
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180418-asa3
    label: psirt@cisco.com
  - url: 'http://www.securitytracker.com/id/1040725'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://ics-cert.us-cert.gov/advisories/ICSA-18-184-01'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180418-asa3
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.04132
epssPercentile: 0.90398
ingestedAt: '2026-08-11T19:48:25.574Z'
---

## Overview

A vulnerability in the Transport Layer Security (TLS) library of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a reload of the affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient validation of user-supplied input. An attacker could exploit this vulnerability by sending a malicious TLS message to an interface enabled for Secure Layer Socket (SSL) services on an affected device. Messages using SSL Version 3 (SSLv3) or SSL Version 2 (SSLv2) cannot be be used to exploit this vulnerability. An exploit could allow the attacker to cause a buffer underflow, triggering a crash on an affected device. This vulnerability affects Cisco ASA Software and Cisco FTD Software that is running on the following Cisco products: Adaptive Security Virtual Appliance (ASAv), Firepower Threat Defense Virtual (FTDv), Firepower 2100 Series Security Appliance. Cisco Bug IDs: CSCve18902, CSCve34335, CSCve38446.

## Affected

- `adaptive_security_appliance_software = 9.8(1)`
- `adaptive_security_appliance_software = 98.1(1.154)`
- `secure_firewall_threat_defense >= 6.0, < 6.1.0.6`
- `secure_firewall_threat_defense >= 6.2.1, < 6.2.2.1`

## Remediation

Upgrade past the affected range:

- `secure_firewall_threat_defense 6.2.2.1`