# CVE-2021-26461: malloc, realloc and memalign implementations are vulnerable to integer wrap-arounds

> Integer wrap-arounds in memory allocation functions allow attackers to cause crashes or execute arbitrary code in NuttX RTOS.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 21 Jun 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-h737-8f7x-38jh

## What is CVE-2021-26461?

CVE-2021-26461 is a critical vulnerability in Apache NuttX, published on 21 Jun 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Apache Nuttx Versions prior to 10.1.0 are vulnerable to integer wrap-around in functions malloc, realloc and memalign. This improper memory assignment can lead to arbitrary memory allocation, resulting in unexpected behavior such as a crash or a remote code injection/execution.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2021-26461?

It affects 1 product.


Products: Apache Nuttx.

## How do I fix CVE-2021-26461?

No fix has been published for CVE-2021-26461 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-26461 being exploited?

There is no known exploitation of CVE-2021-26461 in the wild and no public exploit code.

## Other vulnerabilities in Apache NuttX

- [CVE-2025-47868](https://insights.sbomify.com/CVE-2025-47868/): Apache NuttX RTOS: tools/bdf-converter.: tools/bdf-converter: Fix loop termination condition. (critical 9.8)
- [CVE-2025-47869](https://insights.sbomify.com/CVE-2025-47869/): Apache NuttX RTOS: examples/xmlrpc: Fix calls buffers size. (critical 9.8)
- [CVE-2025-35003](https://insights.sbomify.com/CVE-2025-35003/): Apache NuttX RTOS: NuttX Bluetooth Stack HCI and UART DoS/RCE Vulnerabilities. (critical 9.8)
- [CVE-2020-17529](https://insights.sbomify.com/CVE-2020-17529/): Apache NuttX (incubating) Out of Bound Write from invalid fragmentation offset value specified in the IP header (critical 9.8)
- [CVE-2020-1939](https://insights.sbomify.com/CVE-2020-1939/): Null dereference in Apache NuttX (incubating) (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-26461 and fix it if it is affected.

What it is: CVE-2021-26461 is a critical vulnerability in Apache NuttX, published on 21 Jun 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-2021-26461 in the wild and no public exploit code.

Affected product: Apache NuttX. 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-2021-26461/ (Markdown: https://insights.sbomify.com/CVE-2021-26461/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26461
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26461
- OSV: https://osv.dev/vulnerability/CVE-2021-26461

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-26461/
Summaries are generated and may contain mistakes; the official description above is the record.