# CVE-2020-25681: Memory corruption in dnsmasq

> A heap-based buffer overflow in dnsmasq allows remote attackers to execute arbitrary code or cause denial of service via forged DNS replies.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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:** 20 Jan 2021
- **Updated:** 4 Nov 2025
- **Also known as:** ALPINE-CVE-2020-25681, CLEANSTART-2026-DX67539, DEBIAN-CVE-2020-25681, GHSA-34v3-rp23-947c, UBUNTU-CVE-2020-25681

## What is CVE-2020-25681?

CVE-2020-25681 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 20 Jan 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in dnsmasq before version 2.83. A heap-based buffer overflow was discovered in the way RRSets are sorted before validating with DNSSEC data. An attacker on the network, who can forge DNS replies such as that they are accepted as valid, could use this flaw to cause a buffer overflow with arbitrary data in a heap memory segment, possibly executing code on the machine. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2020-25681?

It affects 3 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Thekelleys Dnsmasq.

## How do I fix CVE-2020-25681?

Upgrade to a fixed version.

## Is CVE-2020-25681 being exploited?

There is no known exploitation of CVE-2020-25681 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-25681 and fix it if it is affected.

What it is: CVE-2020-25681 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 20 Jan 2021. 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-2020-25681 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2020-25681/ (Markdown: https://insights.sbomify.com/CVE-2020-25681/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-25681
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-25681
- OSV: https://osv.dev/vulnerability/CVE-2020-25681

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-25681/
Summaries are generated and may contain mistakes; the official description above is the record.