# CVE-2021-27427: RIOT OS Integer Overflow or Wraparound

> An integer overflow in RIOT OS calloc allows attackers to cause memory corruption, leading to crashes or remote code execution.

- **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-xw8p-6vv6-4c5g

## What is CVE-2021-27427?

CVE-2021-27427 is a high-severity vulnerability in RIOT OS, published on 3 May 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

RIOT OS version 2020.01.1 is vulnerable to integer wrap-around in its implementation of calloc 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-2021-27427?

It affects 1 product.


Products: Riot-Os Riot.

## How do I fix CVE-2021-27427?

No fix has been published for CVE-2021-27427 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-27427 being exploited?

There is no known exploitation of CVE-2021-27427 in the wild and no public exploit code.

## Other vulnerabilities in RIOT OS

- [CVE-2024-32017](https://insights.sbomify.com/CVE-2024-32017/): Buffer overflows in RIOT (critical 9.8)
- [CVE-2023-33975](https://insights.sbomify.com/CVE-2023-33975/): RIOT-OS vulnerable to Out of Bounds Write in _rbuf_add (critical 9.8)
- [CVE-2023-24819](https://insights.sbomify.com/CVE-2023-24819/): RIOT-OS vulnerable to Buffer Overflow during IPHC receive (critical 9.8)
- [CVE-2023-24823](https://insights.sbomify.com/CVE-2023-24823/): RIOT-OS vulnerable to Packet Type Confusion during IPHC send (critical 9.8)
- [CVE-2021-27357](https://insights.sbomify.com/CVE-2021-27357/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27427 and fix it if it is affected.

What it is: CVE-2021-27427 is a high-severity vulnerability in RIOT OS, 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-2021-27427 in the wild and no public exploit code.

Affected product: RIOT OS. 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-2021-27427/ (Markdown: https://insights.sbomify.com/CVE-2021-27427/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27427
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27427
- OSV: https://osv.dev/vulnerability/CVE-2021-27427

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27427/
Summaries are generated and may contain mistakes; the official description above is the record.