---
id: CVE-2023-42441
aliases:
  - GHSA-3hg2-r75x-g69m
  - PYSEC-2023-305
title: Vyper has incorrect re-entrancy lock when key is empty string
summary: Vyper has incorrect re-entrancy lock when key is empty string
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'
vendor: vyper
product: vyper
ecosystem: pip
affected:
  - 'vyper >= 0.2.9, < 0.3.10'
patched:
  - vyper 0.3.10
published: '2023-09-18'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:03.191650148Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-3hg2-r75x-g69m'
references:
  - url: 'https://github.com/vyperlang/vyper/security/advisories/GHSA-3hg2-r75x-g69m'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2023-42441'
  - url: 'https://github.com/vyperlang/vyper/pull/3605'
  - url: >-
      https://github.com/vyperlang/vyper/commit/0b740280c1e3c5528a20d47b29831948ddcc6d83
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-305.yaml
  - url: 'https://github.com/vyperlang/vyper'
tags:
  - osv
  - pip
epss: 0.00514
epssPercentile: 0.42789
ingestedAt: '2026-09-12T03:13:01.646Z'
---

## Overview

### Impact

Locks of the type `@nonreentrant("")` or `@nonreentrant('')` do not produce reentrancy checks at runtime.

```Vyper
@nonreentrant("") # unprotected
@external
def bar():
    pass

@nonreentrant("lock") # protected
@external
def foo():
    pass
```
### Patches

Patched in #3605

### Workarounds

The lock name should be a non-empty string.

### References
_Are there any links users can visit to find out more?_


## Affected packages

- `vyper >= 0.2.9, < 0.3.10`

## Remediation

Upgrade to a patched release:

- `vyper 0.3.10`