# CVE-2021-36754: Denial of service in n/a

> An attacker can crash the PowerDNS Authoritative Server process by sending a specific DNS query, causing a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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:** Yes
- **Published:** 27 Jul 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-g5x7-wx2c-jqff

## What is CVE-2021-36754?

CVE-2021-36754 is a high-severity denial of service vulnerability in n/a, published on 27 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

PowerDNS Authoritative Server 4.5.0 before 4.5.1 allows anybody to crash the process by sending a specific query (QTYPE 65535) that causes an out-of-bounds exception.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2021-36754?

It affects 1 product.


Products: Powerdns Authoritative Server.

## How do I fix CVE-2021-36754?

Upgrade to a fixed version.

## Is CVE-2021-36754 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-36754 exists.

Public exploit code:

- PowerDNS Authoritative Server - Denial of Service (nuclei)

## Other vulnerabilities in n/a

- [CVE-2008-3337](https://insights.sbomify.com/CVE-2008-3337/): Other in n/a (medium 6.4)
- [CVE-2012-0206](https://insights.sbomify.com/CVE-2012-0206/): Denial of service in n/a (medium 5.0)
- [CVE-2019-10203](https://insights.sbomify.com/CVE-2019-10203/): Integer overflow in pdns (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-36754 and fix it if it is affected.

What it is: CVE-2021-36754 is a high-severity denial of service vulnerability in n/a, published on 27 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-36754 exists.

Affected product: n/a. 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-2021-36754/ (Markdown: https://insights.sbomify.com/CVE-2021-36754/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36754
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36754
- OSV: https://osv.dev/vulnerability/CVE-2021-36754

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36754/
Summaries are generated and may contain mistakes; the official description above is the record.