# CVE-2018-5538: Security feature bypass in BIG-IP (DNS)

> Attackers can bypass NOTIFY restrictions on F5 BIG-IP DNS if the notify port is changed from default, allowing unauthorized DNS updates.

- **Severity:** Low 3.7 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Jul 2018
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-vjx8-8j32-57mf

## What is CVE-2018-5538?

CVE-2018-5538 is a low-severity vulnerability in F5 Big-Ip Domain Name System, published on 25 Jul 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

On F5 BIG-IP DNS 13.1.0-13.1.0.7, 12.1.3-12.1.3.5, DNS Express / DNS Zones accept NOTIFY messages on the management interface from source IP addresses not listed in the 'Allow NOTIFY From' configuration parameter when the db variable "dnsexpress.notifyport" is set to any value other than the default of "0".

## Which versions are affected by CVE-2018-5538?

It affects 4 products.


Products: F5 Big-Ip Domain Name System, F5 Big-Ip Global Traffic Manager, F5 Big-Ip Link Controller, F5 Big-Ip Local Traffic Manager.

## How do I fix CVE-2018-5538?

No fix has been published for CVE-2018-5538 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-5538 being exploited?

There is no known exploitation of CVE-2018-5538 in the wild and no public exploit code.

## Other vulnerabilities in F5 Big-Ip Domain Name System

- [CVE-2022-23013](https://insights.sbomify.com/CVE-2022-23013/): Cross-site scripting in BIG-IP DNS & GTM (high 8.8)
- [CVE-2026-40061](https://insights.sbomify.com/CVE-2026-40061/): iControl REST and tmsh vulnerability (high 8.5)
- [CVE-2022-41787](https://insights.sbomify.com/CVE-2022-41787/): BIG-IP DNS Express vulnerability CVE-2022-41787 (high 7.5)
- [CVE-2021-23032](https://insights.sbomify.com/CVE-2021-23032/): Denial of service in BIG-IP DNS (high 7.5)
- [CVE-2020-27717](https://insights.sbomify.com/CVE-2020-27717/): Denial of service in BIG-IP DNS (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-5538 and fix it if it is affected.

What it is: CVE-2018-5538 is a low-severity vulnerability in F5 Big-Ip Domain Name System, published on 25 Jul 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-2018-5538 in the wild and no public exploit code.

Affected product: F5 Big-Ip Domain Name System. 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-2018-5538/ (Markdown: https://insights.sbomify.com/CVE-2018-5538/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-5538
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-5538
- OSV: https://osv.dev/vulnerability/CVE-2018-5538

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-5538/
Summaries are generated and may contain mistakes; the official description above is the record.