# CVE-2021-3573: Use after free in kernel

> A local privileged user can exploit a use-after-free in the Linux kernel HCI subsystem to crash the system or escalate privileges.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Aug 2021
- **Updated:** 3 Aug 2024
- **Also known as:** AZL-6574, DEBIAN-CVE-2021-3573, GHSA-73pg-2qfc-2cfm, UBUNTU-CVE-2021-3573

## What is CVE-2021-3573?

CVE-2021-3573 is a medium-severity use after free vulnerability in Fedoraproject Fedora, published on 13 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A use-after-free in function hci_sock_bound_ioctl() of the Linux kernel HCI subsystem was found in the way user calls ioct HCIUNBLOCKADDR or other way triggers race condition of the call hci_unregister_dev() together with one of the calls hci_sock_blacklist_add(), hci_sock_blacklist_del(), hci_get_conn_info(), hci_get_auth_info(). A privileged local user could use this flaw to crash the system or escalate their privileges on the system. This flaw affects the Linux kernel versions prior to 5.13-rc5.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2021-3573?

It affects 3 products.


Products: Fedoraproject Fedora, Linux kernel, Redhat Enterprise Linux.

## How do I fix CVE-2021-3573?

Apply the vendor's patch.

## Is CVE-2021-3573 being exploited?

There is no known exploitation of CVE-2021-3573 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3573 and fix it if it is affected.

What it is: CVE-2021-3573 is a medium-severity use after free vulnerability in Fedoraproject Fedora, published on 13 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3573 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. 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-2021-3573/ (Markdown: https://insights.sbomify.com/CVE-2021-3573/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3573
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3573
- OSV: https://osv.dev/vulnerability/CVE-2021-3573

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3573/
Summaries are generated and may contain mistakes; the official description above is the record.