# CVE-2020-5591: Denial of service in XACK DNS

> Remote attackers can cause denial of service or use the resolver for reflection attacks, affecting XACK DNS users.

- **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:** No
- **Published:** 5 Jun 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-rgx8-jrmw-j2jr

## What is CVE-2020-5591?

CVE-2020-5591 is a high-severity denial of service vulnerability in XACK, Inc. XACK DNS, published on 5 Jun 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

XACK DNS 1.11.0 to 1.11.4, 1.10.0 to 1.10.8, 1.8.0 to 1.8.23, 1.7.0 to 1.7.18, and versions before 1.7.0 allow remote attackers to cause a denial of service condition resulting in degradation of the recursive resolver's performance or compromising the recursive resolver as a reflector in a reflection attack.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2020-5591?

It affects 1 product.


Products: Xack Xack Dns.

## How do I fix CVE-2020-5591?

No fix has been published for CVE-2020-5591 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-5591 being exploited?

There is no known exploitation of CVE-2020-5591 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-5591 and fix it if it is affected.

What it is: CVE-2020-5591 is a high-severity denial of service vulnerability in XACK, Inc. XACK DNS, published on 5 Jun 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-2020-5591 in the wild and no public exploit code.

Affected product: XACK, Inc. XACK DNS. 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-2020-5591/ (Markdown: https://insights.sbomify.com/CVE-2020-5591/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-5591
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-5591
- OSV: https://osv.dev/vulnerability/CVE-2020-5591

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-5591/
Summaries are generated and may contain mistakes; the official description above is the record.