# CVE-2020-25685: Other in dnsmasq

> An off-path attacker can forge DNS replies due to weak hashing, enabling cache poisoning attacks against dnsmasq users.

- **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-2020-25685, CLEANSTART-2026-CW75331, DEBIAN-CVE-2020-25685, GHSA-9gxq-wfg7-72x4, UBUNTU-CVE-2020-25685

## What is CVE-2020-25685?

CVE-2020-25685 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 getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. 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-326 (Inadequate Encryption Strength)

## Which versions are affected by CVE-2020-25685?

It affects 4 products.


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

## How do I fix CVE-2020-25685?

Upgrade to a fixed version.

## Is CVE-2020-25685 being exploited?

There is no known exploitation of CVE-2020-25685 in the wild and no public exploit code.

## 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-2020-25685 and fix it if it is affected.

What it is: CVE-2020-25685 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-2020-25685 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-2020-25685/ (Markdown: https://insights.sbomify.com/CVE-2020-25685/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-25685
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-25685
- OSV: https://osv.dev/vulnerability/CVE-2020-25685

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-25685/
Summaries are generated and may contain mistakes; the official description above is the record.