# CVE-2020-12667: Denial of service in n/a

> Attackers can cause traffic amplification and denial of service in Knot Resolver by sending crafted DNS answers with random subdomains.

- **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:** 19 May 2020
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-12667, GHSA-2gpj-6wgq-8636, UBUNTU-CVE-2020-12667

## What is CVE-2020-12667?

CVE-2020-12667 is a high-severity denial of service vulnerability in n/a, published on 19 May 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Knot Resolver before 5.1.1 allows traffic amplification via a crafted DNS answer from an attacker-controlled server, aka an "NXNSAttack" issue. This is triggered by random subdomains in the NSDNAME in NS records.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-12667?

It affects 1 product.


Products: Nic Knot Resolver.

## How do I fix CVE-2020-12667?

Upgrade to a fixed version.

## Is CVE-2020-12667 being exploited?

There is no known exploitation of CVE-2020-12667 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2023-46317](https://insights.sbomify.com/CVE-2023-46317/): Denial of service in n/a (high 7.5)
- [CVE-2023-26249](https://insights.sbomify.com/CVE-2023-26249/): Denial of service in n/a (high 7.5)
- [CVE-2021-40083](https://insights.sbomify.com/CVE-2021-40083/): Denial of service in n/a (high 7.5)
- [CVE-2018-1110](https://insights.sbomify.com/CVE-2018-1110/): Denial of service in knot-resolver (high 7.5)
- [CVE-2018-10920](https://insights.sbomify.com/CVE-2018-10920/): Other in knot-resolver (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-12667 and fix it if it is affected.

What it is: CVE-2020-12667 is a high-severity denial of service vulnerability in n/a, published on 19 May 2020. 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-2020-12667 in the wild and no public exploit code.

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-2020-12667/ (Markdown: https://insights.sbomify.com/CVE-2020-12667/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-12667
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-12667
- OSV: https://osv.dev/vulnerability/CVE-2020-12667

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-12667/
Summaries are generated and may contain mistakes; the official description above is the record.