# CVE-2018-0231: Denial of service in Cisco Adaptive Security Appliance

> Remote unauthenticated attackers can cause a denial of service on Cisco ASA and FTD devices by sending malicious TLS messages, triggering a crash.

- **Severity:** High 8.6 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Apr 2018
- **Updated:** 29 Nov 2024
- **Also known as:** GHSA-wq2j-24r5-rxj2

## What is CVE-2018-0231?

CVE-2018-0231 is a high-severity denial of service vulnerability in Cisco Adaptive Security Appliance Software, published on 19 Apr 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-787 (Out-of-bounds Write), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2018-0231?

It affects 2 products.


Products: Cisco Adaptive Security Appliance Software, Cisco Secure Firewall Threat Defense.

## How do I fix CVE-2018-0231?

No fix has been published for CVE-2018-0231 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-0231 being exploited?

There is no known exploitation of CVE-2018-0231 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Adaptive Security Appliance Software

- [CVE-2025-20333](https://insights.sbomify.com/CVE-2025-20333/): Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow (critical 9.9, exploited in the wild)
- [CVE-2016-6366](https://insights.sbomify.com/CVE-2016-6366/): Cisco Adaptive Security Appliance (ASA) SNMP Buffer Overflow (high 8.8, exploited in the wild)
- [CVE-2026-20349](https://insights.sbomify.com/CVE-2026-20349/): Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection (high 8.6, exploited in the wild)
- [CVE-2024-20353](https://insights.sbomify.com/CVE-2024-20353/): Cisco ASA and FTD Denial of Service (high 8.6, exploited in the wild)
- [CVE-2016-6367](https://insights.sbomify.com/CVE-2016-6367/): Cisco Adaptive Security Appliance (ASA) CLI Remote Code Execution (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-0231 and fix it if it is affected.

What it is: CVE-2018-0231 is a high-severity denial of service vulnerability in Cisco Adaptive Security Appliance Software, published on 19 Apr 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-0231 in the wild and no public exploit code.

Affected product: Cisco Adaptive Security Appliance Software. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-0231/ (Markdown: https://insights.sbomify.com/CVE-2018-0231/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-0231
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-0231
- OSV: https://osv.dev/vulnerability/CVE-2018-0231

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-0231/
Summaries are generated and may contain mistakes; the official description above is the record.