# CVE-2009-4008: Denial of service in n/a

> Remote attackers can cause a denial of service in Unbound DNS resolver by sending crafted queries to signed zones.

- **Severity:** Medium 5.0 (`AV:N/AC:L/Au:N/C:N/I:N/A:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Jun 2011
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2009-4008, DSA-2243-1, GHSA-cjjv-pc59-mghf

## What is CVE-2009-4008?

CVE-2009-4008 is a medium-severity denial of service vulnerability in Nlnetlabs Unbound, published on 2 Jun 2011. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Unbound before 1.4.4 does not send responses for signed zones after mishandling an unspecified query, which allows remote attackers to cause a denial of service (DNSSEC outage) via a crafted query.

Weakness: CWE-399

## Which versions are affected by CVE-2009-4008?

It affects 1 product.


Products: Nlnetlabs Unbound.

## How do I fix CVE-2009-4008?

Upgrade to a fixed version.

## Is CVE-2009-4008 being exploited?

There is no known exploitation of CVE-2009-4008 in the wild and no public exploit code.

## Other vulnerabilities in Nlnetlabs Unbound

- [CVE-2026-81642](https://insights.sbomify.com/CVE-2026-81642/): Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY (critical 9.1)
- [CVE-2026-33278](https://insights.sbomify.com/CVE-2026-33278/): Possible arbitrary code execution during DNSSEC validation (critical 9.1)
- [CVE-2026-42944](https://insights.sbomify.com/CVE-2026-42944/): Heap overflow with multiple NSID, COOKIE, PADDING EDNS options (high 8.7)
- [CVE-2026-42959](https://insights.sbomify.com/CVE-2026-42959/): Crash during DNSSEC validation of malicious content (high 8.7)
- [CVE-2026-82717](https://insights.sbomify.com/CVE-2026-82717/): CNAME synthesis could lead to heap corruption (high 8.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2009-4008 and fix it if it is affected.

What it is: CVE-2009-4008 is a medium-severity denial of service vulnerability in Nlnetlabs Unbound, published on 2 Jun 2011. 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-2009-4008 in the wild and no public exploit code.

Affected product: Nlnetlabs Unbound. 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-2009-4008/ (Markdown: https://insights.sbomify.com/CVE-2009-4008/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2009-4008
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2009-4008
- OSV: https://osv.dev/vulnerability/CVE-2009-4008

---
From sbomify Insights: https://insights.sbomify.com/CVE-2009-4008/
Summaries are generated and may contain mistakes; the official description above is the record.