# CVE-2011-4528: Use after free in n/a

> Remote attackers can crash the Unbound DNS resolver by sending crafted responses with duplicate CNAME records, causing a denial of service.

- **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:** 20 Dec 2011
- **Updated:** 7 Aug 2024
- **Also known as:** DEBIAN-CVE-2011-4528, GHSA-q376-m379-55x8

## What is CVE-2011-4528?

CVE-2011-4528 is a medium-severity use after free vulnerability in n/a, published on 20 Dec 2011. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Unbound before 1.4.13p2 attempts to free unallocated memory during processing of duplicate CNAME records in a signed zone, which allows remote DNS servers to cause a denial of service (daemon crash) via a crafted response.

Weakness: CWE-399

## Which versions are affected by CVE-2011-4528?

It affects 1 product.


Products: Unbound Unbound.

## How do I fix CVE-2011-4528?

Upgrade to a fixed version.

## Is CVE-2011-4528 being exploited?

There is no known exploitation of CVE-2011-4528 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2011-4869](https://insights.sbomify.com/CVE-2011-4869/): Denial of service in n/a (high 7.8)
- [CVE-2012-1192](https://insights.sbomify.com/CVE-2012-1192/): The resolver in Unbound before 1.4.11 overwrites cached server names and TTL values in NS records during the processing of a response to an (medium 6.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2011-4528 and fix it if it is affected.

What it is: CVE-2011-4528 is a medium-severity use after free vulnerability in n/a, published on 20 Dec 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-2011-4528 in the wild and no public exploit code.

Affected product: n/a. 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-2011-4528/ (Markdown: https://insights.sbomify.com/CVE-2011-4528/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2011-4528
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2011-4528
- OSV: https://osv.dev/vulnerability/CVE-2011-4528

---
From sbomify Insights: https://insights.sbomify.com/CVE-2011-4528/
Summaries are generated and may contain mistakes; the official description above is the record.