---
id: CVE-2023-32058
aliases:
  - GHSA-6r8q-pfpv-7cgj
  - PYSEC-2023-78
title: Vyper vulnerable to integer overflow in loop
summary: Vyper vulnerable to integer overflow in loop
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: vyper
product: vyper
ecosystem: pip
affected:
  - vyper < 0.3.8
patched:
  - vyper 0.3.8
published: '2023-05-12'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:01.254556464Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-6r8q-pfpv-7cgj'
references:
  - url: 'https://github.com/vyperlang/vyper/security/advisories/GHSA-6r8q-pfpv-7cgj'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2023-32058'
  - url: >-
      https://github.com/vyperlang/vyper/commit/3de1415ee77a9244eb04bdb695e249d3ec9ed868
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-78.yaml
  - url: 'https://github.com/vyperlang/vyper'
tags:
  - osv
  - pip
epss: 0.00913
epssPercentile: 0.58589
ingestedAt: '2026-09-12T03:13:01.667Z'
---

## Overview

### Impact

Due to missing overflow check for loop variables, by assigning the iterator of a loop to a variable, it is possible to overflow the type of the latter.

In the following example, calling `test` returns `354`, meaning that the variable `a` did store `354` a value out of bound for the type `uint8`.

```Vyper
@external
def test() -> uint16:
    x:uint8 = 255
    a:uint8 = 0
    for i in range(x, x+100):
        a = i
    return convert(a,uint16)
```

The issue seems to happen only in loops of type `for i in range(a, a + N)` as in loops of type `for i in range(start, stop)` and `for i in range(stop)`, the compiler is able to raise a `TypeMismatch` when trying to overflow the variable.

thanks to @trocher for reporting

### Patches

patched in 3de1415ee77a9244eb04bdb695e249d3ec9ed868

### Workarounds

 

## Affected packages

- `vyper < 0.3.8`

## Remediation

Upgrade to a patched release:

- `vyper 0.3.8`