# CVE-2019-3806: Security feature bypass in pdns-recursor

> Attackers can bypass Lua-based security policies in PowerDNS Recursor by sending TCP queries under specific configurations.

- **Severity:** Medium 5.4 (`CVSS:3.0/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 29 Jan 2019
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2019-3806, GHSA-3jqp-f4vw-9c87, UBUNTU-CVE-2019-3806

## What is CVE-2019-3806?

CVE-2019-3806 is a medium-severity vulnerability in Powerdns Recursor, published on 29 Jan 2019. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

An issue has been found in PowerDNS Recursor versions after 4.1.3 before 4.1.9 where Lua hooks are not properly applied to queries received over TCP in some specific combination of settings, possibly bypassing security policies enforced using Lua.

Weakness: CWE-358 (Improperly Implemented Security Check for Standard)

## Which versions are affected by CVE-2019-3806?

It affects 1 product.


Products: Powerdns Recursor.

## How do I fix CVE-2019-3806?

Upgrade to a fixed version.

## Is CVE-2019-3806 being exploited?

There is no known exploitation of CVE-2019-3806 in the wild and no public exploit code.

## Other vulnerabilities in Powerdns Recursor

- [CVE-2009-4009](https://insights.sbomify.com/CVE-2009-4009/): Memory corruption in n/a (critical 10.0)
- [CVE-2020-10030](https://insights.sbomify.com/CVE-2020-10030/): Memory corruption in n/a (high 8.8)
- [CVE-2025-59023](https://insights.sbomify.com/CVE-2025-59023/): Crafted delegations or IP fragments can poison cached delegations in Recursor (high 8.2)
- [CVE-2025-59030](https://insights.sbomify.com/CVE-2025-59030/): Insufficient validation of incoming notifies over TCP can lead to a denial of service in Recursor (high 7.5)
- [CVE-2023-22617](https://insights.sbomify.com/CVE-2023-22617/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-3806 and fix it if it is affected.

What it is: CVE-2019-3806 is a medium-severity vulnerability in Powerdns Recursor, published on 29 Jan 2019. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2019-3806 in the wild and no public exploit code.

Affected product: Powerdns Recursor. 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-2019-3806/ (Markdown: https://insights.sbomify.com/CVE-2019-3806/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-3806
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-3806
- OSV: https://osv.dev/vulnerability/CVE-2019-3806

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-3806/
Summaries are generated and may contain mistakes; the official description above is the record.