---
id: CVE-2023-30837
aliases:
  - GHSA-mgv8-gggw-mrg6
  - PYSEC-2023-76
title: vyper vulnerable to storage allocator overflow
summary: vyper vulnerable to storage allocator overflow
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
vendor: vyper
product: vyper
ecosystem: pip
affected:
  - vyper < 0.3.8
patched:
  - vyper 0.3.8
published: '2023-05-05'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:01.648781390Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-mgv8-gggw-mrg6'
references:
  - url: 'https://github.com/vyperlang/vyper/security/advisories/GHSA-mgv8-gggw-mrg6'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2023-30837'
  - url: >-
      https://github.com/vyperlang/vyper/commit/0bb7203b584e771b23536ba065a6efda457161bb
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-76.yaml
  - url: 'https://github.com/vyperlang/vyper'
tags:
  - osv
  - pip
epss: 0.00697
epssPercentile: 0.51028
ingestedAt: '2026-09-12T03:13:01.711Z'
---

## Overview

### Impact
The storage allocator does not guard against allocation overflows. This can result in vulnerabilities like the following:
```vyper
owner: public(address)
take_up_some_space: public(uint256[10])
buffer: public(uint256[max_value(uint256)])

@external
def initialize():
    self.owner = msg.sender

@external
def foo(idx: uint256, data: uint256):
    self.buffer[idx] = data
```
Per @toonvanhove, "An attacker can overwrite the owner variable by calling this contract with calldata: `0x04bc52f8 fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff5 ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff` (spaces inserted for readability)
`0x04bc52f8` is the selector for `foo(uint256, uint256)`, and the last argument `fff...fff` is the new value for the owner variable."

### Patches
patched in 0bb7203b584e771b23536ba065a6efda457161bb

### Workarounds
_Is there a way for users to fix or remediate the vulnerability without upgrading?_

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


## Affected packages

- `vyper < 0.3.8`

## Remediation

Upgrade to a patched release:

- `vyper 0.3.8`