# CVE-2021-22945: Use after free in https://github.com/curl/curl

> A use-after-free flaw in libcurl's MQTT implementation allows attackers to cause crashes or potentially execute arbitrary code.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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:** 23 Sep 2021
- **Updated:** 14 Oct 2026
- **Also known as:** ALPINE-CVE-2021-22945, AZL-6368, CLEANSTART-2026-YT27832, CURL-CVE-2021-22945, DEBIAN-CVE-2021-22945, GHSA-22mx-9r92-42g8, JLSEC-2025-29, UBUNTU-CVE-2021-22945

## What is CVE-2021-22945?

CVE-2021-22945 is a critical use after free vulnerability in Apple Macos, published on 23 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

When sending data to an MQTT server, libcurl <= 7.73.0 and 7.78.0 could in some circumstances erroneously keep a pointer to an already freed memory area and both use that again in a subsequent call to send data and also free it *again*.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2021-22945?

It affects 17 products.


Products: Apple Macos, Debian Debian Linux, Fedoraproject Fedora, Haxx Libcurl, Netapp Cloud Backup, Netapp Clustered Data Ontap, Netapp H300e Firmware, Netapp H300s Firmware, Netapp H410s Firmware, Netapp H500e Firmware, Netapp H500s Firmware, Netapp H700e Firmware, Netapp H700s Firmware, Netapp Solidfire Baseboard Management Controller Firmware, Oracle Mysql Server, Siemens Sinec Ins, Splunk Universal Forwarder.

## How do I fix CVE-2021-22945?

Upgrade to a fixed version.

## Is CVE-2021-22945 being exploited?

There is no known exploitation of CVE-2021-22945 in the wild and no public exploit code.

## Other vulnerabilities in Apple Macos

- [CVE-2026-65400](https://insights.sbomify.com/CVE-2026-65400/): Apple macOS Improper Authentication (critical 9.8, exploited in the wild)
- [CVE-2024-44146](https://insights.sbomify.com/CVE-2024-44146/): Security feature bypass in macOS (critical 10.0)
- [CVE-2024-44148](https://insights.sbomify.com/CVE-2024-44148/): Security feature bypass in macOS (critical 10.0)
- [CVE-2023-38586](https://insights.sbomify.com/CVE-2023-38586/): Security feature bypass in macOS (critical 10.0)
- [CVE-2023-40455](https://insights.sbomify.com/CVE-2023-40455/): Security feature bypass in macOS (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-22945 and fix it if it is affected.

What it is: CVE-2021-22945 is a critical use after free vulnerability in Apple Macos, published on 23 Sep 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-2021-22945 in the wild and no public exploit code.

Affected product: Apple Macos. 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-2021-22945/ (Markdown: https://insights.sbomify.com/CVE-2021-22945/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-22945
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-22945
- OSV: https://osv.dev/vulnerability/CVE-2021-22945

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-22945/
Summaries are generated and may contain mistakes; the official description above is the record.