# CVE-2020-25686: Other in dnsmasq

> An off-path attacker can reduce the effort required to forge DNS replies, compromising data integrity in dnsmasq.

- **Severity:** Low 3.7 (`CVSS:3.1/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:** Yes
- **Published:** 20 Jan 2021
- **Updated:** 4 Nov 2025
- **Also known as:** ALPINE-CVE-2020-25686, CLEANSTART-2026-AH64015, DEBIAN-CVE-2020-25686, GHSA-9xp3-mp9c-47rf, UBUNTU-CVE-2020-25686

## What is CVE-2020-25686?

CVE-2020-25686 is a low-severity 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. When receiving a query, dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default, a maximum of 150 pending queries can be sent to upstream servers, so there can be at most 150 queries for the same name. This flaw allows an off-path attacker on the network to substantially reduce the number of attempts that it would have to perform to forge a reply and have it accepted by dnsmasq. This issue is mentioned in the "Birthday Attacks" section of RFC5452. If chained with CVE-2020-25684, the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.

Weakness: CWE-290 (Authentication Bypass by Spoofing), CWE-358 (Improperly Implemented Security Check for Standard)

## Which versions are affected by CVE-2020-25686?

It affects 4 products.


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

## How do I fix CVE-2020-25686?

Upgrade to a fixed version.

## Is CVE-2020-25686 being exploited?

There is no known exploitation of CVE-2020-25686 in the wild and no public exploit code.

Public exploit code:

- DNSpooq - dnsmasq cache poisoning (CVE-2020-25686, CVE-2020-25684, CVE-2020-25685) (github_poc): https://github.com/knqyf263/dnspooq

## Other vulnerabilities in Debian Debian Linux

- [CVE-2026-7473](https://insights.sbomify.com/CVE-2026-7473/): Arista Extensible Operating System Incomplete Comparison with Missing Factors (medium 6.9, exploited in the wild)
- [CVE-2015-8236](https://insights.sbomify.com/CVE-2015-8236/): Privilege escalation in n/a (critical 10.0)
- [CVE-2020-10188](https://insights.sbomify.com/CVE-2020-10188/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-18017](https://insights.sbomify.com/CVE-2017-18017/): Use after free in n/a (critical 9.8)
- [CVE-2017-14491](https://insights.sbomify.com/CVE-2017-14491/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-25686 and fix it if it is affected.

What it is: CVE-2020-25686 is a low-severity 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-2020-25686 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-2020-25686/ (Markdown: https://insights.sbomify.com/CVE-2020-25686/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-25686
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-25686
- OSV: https://osv.dev/vulnerability/CVE-2020-25686

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-25686/
Summaries are generated and may contain mistakes; the official description above is the record.