# CVE-2021-43400: Use after free in n/a

> A use-after-free in BlueZ allows attackers to execute code or cause denial of service via a crafted Bluetooth disconnection during D-Bus processing.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 4 Nov 2021
- **Updated:** 4 Nov 2025
- **Also known as:** DEBIAN-CVE-2021-43400, GHSA-xgf8-98pj-cm5c, OESA-2022-1527, UBUNTU-CVE-2021-43400

## What is CVE-2021-43400?

CVE-2021-43400 is a critical use after free vulnerability in Debian Debian Linux, published on 4 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in gatt-database.c in BlueZ 5.61. A use-after-free can occur when a client disconnects during D-Bus processing of a WriteValue call.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-43400?

It affects 2 products.


Products: Bluez Bluez, Debian Debian Linux.

## How do I fix CVE-2021-43400?

Apply the vendor's patch.

## Is CVE-2021-43400 being exploited?

There is no known exploitation of CVE-2021-43400 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2024-8805](https://insights.sbomify.com/CVE-2024-8805/): BlueZ HID over GATT Profile Improper Access Control Remote Code Execution Vulnerability (high 8.8)
- [CVE-2022-39176](https://insights.sbomify.com/CVE-2022-39176/): Information disclosure in n/a (high 8.8)
- [CVE-2022-39177](https://insights.sbomify.com/CVE-2022-39177/): Denial of service in n/a (high 8.8)
- [CVE-2022-0204](https://insights.sbomify.com/CVE-2022-0204/): Memory corruption in bluez (high 8.8)
- [CVE-2019-8922](https://insights.sbomify.com/CVE-2019-8922/): Memory corruption in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43400 and fix it if it is affected.

What it is: CVE-2021-43400 is a critical use after free vulnerability in Debian Debian Linux, published on 4 Nov 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-2021-43400 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-2021-43400/ (Markdown: https://insights.sbomify.com/CVE-2021-43400/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43400
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43400
- OSV: https://osv.dev/vulnerability/CVE-2021-43400

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43400/
Summaries are generated and may contain mistakes; the official description above is the record.