# CVE-2021-27431: ARM CMSIS RTOS2 Integer Overflow or Wraparound

> An integer overflow in ARM CMSIS RTOS2 allows attackers to trigger arbitrary memory allocation, potentially leading to code execution or system 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-fphh-2884-975g

## What is CVE-2021-27431?

CVE-2021-27431 is a high-severity vulnerability in ARM CMSIS RTOS2, 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 CMSIS RTOS2 versions prior to 2.1.3 are vulnerable to integer wrap-around inosRtxMemoryAlloc (local malloc equivalent) function, which can lead to arbitrary memory allocation, resulting in unexpected behavior such as a crash or injected code execution.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2021-27431?

It affects 1 product.


Products: Arm Cmsis-Rtos.

## How do I fix CVE-2021-27431?

No fix has been published for CVE-2021-27431 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-27431 being exploited?

There is no known exploitation of CVE-2021-27431 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27431 and fix it if it is affected.

What it is: CVE-2021-27431 is a high-severity vulnerability in ARM CMSIS RTOS2, published on 3 May 2022. 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-2021-27431 in the wild and no public exploit code.

Affected product: ARM CMSIS RTOS2. 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-2021-27431/ (Markdown: https://insights.sbomify.com/CVE-2021-27431/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27431
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27431
- OSV: https://osv.dev/vulnerability/CVE-2021-27431

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-27431/
Summaries are generated and may contain mistakes; the official description above is the record.