# CVE-2021-41688: Use after free in n/a

> A double free vulnerability in DCMTK's dcmqrdb program allows attackers to cause a denial of service via specific requests.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Jun 2022
- **Updated:** 3 Nov 2025
- **Also known as:** DEBIAN-CVE-2021-41688, GHSA-fwff-cx6h-wxmq, UBUNTU-CVE-2021-41688

## What is CVE-2021-41688?

CVE-2021-41688 is a high-severity use after free vulnerability in n/a, published on 28 Jun 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

DCMTK through 3.6.6 does not handle memory free properly. The object in the program is free but its address is still used in other locations. Sending specific requests to the dcmqrdb program will incur a double free. An attacker can use it to launch a DoS attack.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2021-41688?

It affects 1 product.


Products: Offis Dcmtk.

## How do I fix CVE-2021-41688?

Apply the vendor's patch.

## Is CVE-2021-41688 being exploited?

There is no known exploitation of CVE-2021-41688 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2024-47796](https://insights.sbomify.com/CVE-2024-47796/): Memory corruption in DCMTK (high 8.4)
- [CVE-2024-52333](https://insights.sbomify.com/CVE-2024-52333/): Memory corruption in DCMTK (high 8.4)
- [CVE-2024-27628](https://insights.sbomify.com/CVE-2024-27628/): Memory corruption in n/a (high 8.1)
- [CVE-2022-43272](https://insights.sbomify.com/CVE-2022-43272/): Denial of service in n/a (high 7.5)
- [CVE-2021-41687](https://insights.sbomify.com/CVE-2021-41687/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-41688 and fix it if it is affected.

What it is: CVE-2021-41688 is a high-severity use after free vulnerability in n/a, published on 28 Jun 2022. 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-2021-41688 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-2021-41688/ (Markdown: https://insights.sbomify.com/CVE-2021-41688/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41688
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41688
- OSV: https://osv.dev/vulnerability/CVE-2021-41688

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-41688/
Summaries are generated and may contain mistakes; the official description above is the record.