# CVE-2021-3581: Buffer Access with Incorrect Length Value in zephyr

> An attacker can exploit a buffer access flaw in Zephyr RTOS to cause memory corruption, potentially leading to code execution or denial of service.

- **Severity:** High 7.0 (`CVSS:3.1/AV:P/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 5 Oct 2021
- **Updated:** 16 Sep 2024

## What is CVE-2021-3581?

CVE-2021-3581 is a high-severity memory corruption vulnerability in Zephyrproject Zephyr, published on 5 Oct 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Buffer Access with Incorrect Length Value in zephyr. Zephyr versions >= >=2.5.0 contain Buffer Access with Incorrect Length Value (CWE-805). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8q65-5gqf-fmw5

Weakness: CWE-1284 (Improper Validation of Specified Quantity in Input), CWE-805 (Buffer Access with Incorrect Length Value)

## Which versions are affected by CVE-2021-3581?

It affects 1 product.


Products: Zephyrproject Zephyr.

## How do I fix CVE-2021-3581?

No fix has been published for CVE-2021-3581 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-3581 being exploited?

There is no known exploitation of CVE-2021-3581 in the wild and no public exploit code.

## Other vulnerabilities in Zephyrproject Zephyr

- [CVE-2026-5067](https://insights.sbomify.com/CVE-2026-5067/): Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key (critical 9.8)
- [CVE-2022-3806](https://insights.sbomify.com/CVE-2022-3806/): Bluetooth HCI Error Handling Double Free (critical 9.8)
- [CVE-2017-14199](https://insights.sbomify.com/CVE-2017-14199/): Memory corruption in getaddrinfo (critical 9.8)
- [CVE-2018-1000800](https://insights.sbomify.com/CVE-2018-1000800/): Null dereference in n/a (critical 9.8)
- [CVE-2021-3329](https://insights.sbomify.com/CVE-2021-3329/): DOS: Incorrect handling of the initial HCI ACL_MTU handshake packet leads to crash of bluetooth host layer (critical 9.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3581 and fix it if it is affected.

What it is: CVE-2021-3581 is a high-severity memory corruption vulnerability in Zephyrproject Zephyr, published on 5 Oct 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-3581 in the wild and no public exploit code.

Affected product: Zephyrproject Zephyr. 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-2021-3581/ (Markdown: https://insights.sbomify.com/CVE-2021-3581/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3581
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3581
- OSV: https://osv.dev/vulnerability/CVE-2021-3581

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3581/
Summaries are generated and may contain mistakes; the official description above is the record.