# CVE-2021-27435: ARM mbed Integer Overflow or Wraparound

> An integer overflow in ARM mbed's malloc_wrapper allows arbitrary memory allocation, potentially leading to remote code execution or crashes.

- **Severity:** High 7.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 3 May 2022
- **Updated:** 16 Apr 2025
- **Also known as:** GHSA-8g7w-r5wc-r97f

## What is CVE-2021-27435?

CVE-2021-27435 is a high-severity vulnerability in ARM mbed, published on 3 May 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ARM mbed product Version 6.3.0 is vulnerable to integer wrap-around in malloc_wrapper function, which 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-2021-27435?

It affects 1 product.


Products: Arm Mbed.

## How do I fix CVE-2021-27435?

No fix has been published for CVE-2021-27435 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-27435 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-27435 exists.

## Other vulnerabilities in ARM mbed

- [CVE-2024-48981](https://insights.sbomify.com/CVE-2024-48981/): Memory corruption in n/a (high 7.5)
- [CVE-2024-48982](https://insights.sbomify.com/CVE-2024-48982/): Integer overflow in n/a (high 7.5)
- [CVE-2024-48983](https://insights.sbomify.com/CVE-2024-48983/): Integer overflow in n/a (high 7.5)
- [CVE-2024-48985](https://insights.sbomify.com/CVE-2024-48985/): Memory corruption in n/a (high 7.5)
- [CVE-2024-48986](https://insights.sbomify.com/CVE-2024-48986/): Memory corruption in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27435 and fix it if it is affected.

What it is: CVE-2021-27435 is a high-severity vulnerability in ARM mbed, published on 3 May 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-27435 exists.

Affected product: ARM mbed. 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-2021-27435/ (Markdown: https://insights.sbomify.com/CVE-2021-27435/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27435
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27435
- OSV: https://osv.dev/vulnerability/CVE-2021-27435

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27435/
Summaries are generated and may contain mistakes; the official description above is the record.