# CVE-2023-42441: Vyper has incorrect re-entrancy lock when key is empty string

> Vyper compiler fails to enforce reentrancy locks when the lock name is an empty string, allowing attackers to bypass security checks in smart contracts.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Sep 2023
- **Updated:** 24 Sep 2024
- **Also known as:** GHSA-3hg2-r75x-g69m, PYSEC-2023-305

## What is CVE-2023-42441?

CVE-2023-42441 is a medium-severity vulnerability in vyperlang vyper, published on 18 Sep 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Vyper is a Pythonic Smart Contract Language for the Ethereum Virtual Machine (EVM). Starting in version 0.2.9 and prior to version 0.3.10, locks of the type `@nonreentrant("")` or `@nonreentrant('')` do not produce reentrancy checks at runtime. This issue is fixed in version 0.3.10. As a workaround, ensure the lock name is a non-empty string.

Weakness: CWE-667 (Improper Locking), CWE-833 (Deadlock)

## Which versions are affected by CVE-2023-42441?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `vyper` | PyPI | From 0.2.9 | 0.3.10 |
| `vyper` | PyPI | From 0.2.9 | 0.3.10 |
| `vyper` | PyPI | From 0.2.9 | 0.3.10 |

Products: Vyperlang Vyper.

## How do I fix CVE-2023-42441?

Upgrade vyper to 0.3.10 or later.

## Is CVE-2023-42441 being exploited?

There is no known exploitation of CVE-2023-42441 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-2023-42441 and fix it if it is affected.

What it is: CVE-2023-42441 is a medium-severity vulnerability in vyperlang vyper, published on 18 Sep 2023. 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-2023-42441 in the wild and no public exploit code.

Affected packages and fixed versions:
- vyper (PyPI): affected from 0.2.9; fixed in 0.3.10
- vyper (PyPI): affected from 0.2.9; fixed in 0.3.10
- vyper (PyPI): affected from 0.2.9; fixed in 0.3.10

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-2023-42441/ (Markdown: https://insights.sbomify.com/CVE-2023-42441/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-42441
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-42441
- OSV: https://osv.dev/vulnerability/CVE-2023-42441

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-42441/
Summaries are generated and may contain mistakes; the official description above is the record.