# CVE-2021-41121: Memory corruption in Vyper

> A memory corruption flaw in the Vyper compiler allows attackers to potentially execute arbitrary code via crafted smart contracts.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-xv8x-pr4h-73jv, PYSEC-2021-365

## What is CVE-2021-41121?

CVE-2021-41121 is a high-severity memory corruption vulnerability in vyperlang vyper, published on 6 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Vyper is a Pythonic Smart Contract Language for the EVM. In affected versions when performing a function call inside a literal struct, there is a memory corruption issue that occurs because of an incorrect pointer to the the top of the stack. This issue has been resolved in version 0.3.0.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2021-41121?

3 open source packages ship an affected version, including vyper. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `vyper` | PyPI | All versions | 0.3.0 |
| `vyper` | PyPI | All versions | 0.3.0 |
| `vyper` | PyPI | All versions | 0.3.0 |

Products: Vyperlang Vyper.

## How do I fix CVE-2021-41121?

Upgrade vyper to 0.3.0 or later.

## Is CVE-2021-41121 being exploited?

There is no known exploitation of CVE-2021-41121 in the wild and no public exploit code.

## Other vulnerabilities in vyperlang vyper

- [CVE-2024-24563](https://insights.sbomify.com/CVE-2024-24563/): Vyper array negative index vulnerability (critical 9.8)
- [CVE-2024-24561](https://insights.sbomify.com/CVE-2024-24561/): Vyper bounds check on built-in `slice()` function can be overflowed (critical 9.8)
- [CVE-2023-39363](https://insights.sbomify.com/CVE-2023-39363/): Vyper incorrectly allocated named re-entrancy locks (critical 9.1)
- [CVE-2022-24845](https://insights.sbomify.com/CVE-2022-24845/): Integer bounds error in Vyper (high 8.8)
- [CVE-2022-29255](https://insights.sbomify.com/CVE-2022-29255/): Multiple evaluation of contract address in call in vyper (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-41121 and fix it if it is affected.

What it is: CVE-2021-41121 is a high-severity memory corruption vulnerability in vyperlang vyper, published on 6 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-41121 in the wild and no public exploit code.

Affected packages and fixed versions:
- vyper (PyPI): affected all versions; fixed in 0.3.0
- vyper (PyPI): affected all versions; fixed in 0.3.0
- vyper (PyPI): affected all versions; fixed in 0.3.0

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-2021-41121/ (Markdown: https://insights.sbomify.com/CVE-2021-41121/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41121
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41121
- OSV: https://osv.dev/vulnerability/CVE-2021-41121

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-41121/
Summaries are generated and may contain mistakes; the official description above is the record.