# CVE-2023-46247: Vyper has incorrect storage layout for contracts containing large arrays

> Vyper compiler incorrectly calculates storage slots for large arrays due to floating-point rounding errors, potentially causing memory corruption in smart contracts.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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:** 13 Dec 2023
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-6m97-7527-mh74, PYSEC-2023-307

## What is CVE-2023-46247?

CVE-2023-46247 is a high-severity vulnerability in vyperlang vyper, published on 13 Dec 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). Contracts containing large arrays might underallocate the number of slots they need by 1. Prior to v0.3.8, the calculation to determine how many slots a storage variable needed used `math.ceil(type_.size_in_bytes / 32)`. The intermediate floating point step can produce a rounding error if there are enough bits set in the IEEE-754 mantissa. Roughly speaking, if `type_.size_in_bytes` is large (> 2**46), and slightly less than a power of 2, the calculation can overestimate how many slots are needed by 1. If `type_.size_in_bytes` is slightly more than a power of 2, the calculation can underestimate how many slots are needed by 1. This issue is patched in version 0.3.8.

Weakness: CWE-682 (Incorrect Calculation), CWE-193 (Off-by-one Error)

## Which versions are affected by CVE-2023-46247?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `vyper` | PyPI | All versions | 0.3.8 |
| `vyper` | PyPI | All versions | 0.3.8 |
| `vyper` | PyPI | All versions | 0.3.8 |

Products: Vyperlang Vyper.

## How do I fix CVE-2023-46247?

Upgrade vyper to 0.3.8 or later.

## Is CVE-2023-46247 being exploited?

There is no known exploitation of CVE-2023-46247 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-2023-46247 and fix it if it is affected.

What it is: CVE-2023-46247 is a high-severity vulnerability in vyperlang vyper, published on 13 Dec 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-2023-46247 in the wild and no public exploit code.

Affected packages and fixed versions:
- vyper (PyPI): affected all versions; fixed in 0.3.8
- vyper (PyPI): affected all versions; fixed in 0.3.8
- vyper (PyPI): affected all versions; fixed in 0.3.8

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-2023-46247/ (Markdown: https://insights.sbomify.com/CVE-2023-46247/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-46247
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-46247
- OSV: https://osv.dev/vulnerability/CVE-2023-46247

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-46247/
Summaries are generated and may contain mistakes; the official description above is the record.