# CVE-2024-32646: vyper performs double eval of the slice args when buffer from adhoc locations

> Vyper compiler double-evaluates slice arguments with side effects, potentially allowing unintended code execution 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:** 25 Apr 2024
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-r56x-j438-vw5m, PYSEC-2024-207

## What is CVE-2024-32646?

CVE-2024-32646 is a medium-severity code injection vulnerability in vyperlang vyper, published on 25 Apr 2024. 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. In versions 0.3.10 and prior, using the `slice` builtin can result in a double eval vulnerability when the buffer argument is either `msg.data`, `self.code` or `<address>.code` and either the `start` or `length` arguments have side-effects. It can be easily triggered only with the versions `<0.3.4` as `0.3.4` introduced the unique symbol fence. No vulnerable production contracts were found. Additionally, double evaluation of side-effects should be easily discoverable in client tests. As such, the impact is low. As of time of publication, no fixed versions are available.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2024-32646?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `vyper` | PyPI | All versions | 0.4.0 |
| `vyper` | PyPI | All versions | 0.4.0 |
| `vyper` | PyPI | All versions | 0.4.0 |

Products: Vyperlang Vyper.

## How do I fix CVE-2024-32646?

Upgrade vyper to 0.4.0 or later.

## Is CVE-2024-32646 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-32646 exists.

## 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-2024-32646 and fix it if it is affected.

What it is: CVE-2024-32646 is a medium-severity code injection vulnerability in vyperlang vyper, published on 25 Apr 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-32646 exists.

Affected packages and fixed versions:
- vyper (PyPI): affected all versions; fixed in 0.4.0
- vyper (PyPI): affected all versions; fixed in 0.4.0
- vyper (PyPI): affected all versions; fixed in 0.4.0

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-2024-32646/ (Markdown: https://insights.sbomify.com/CVE-2024-32646/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-32646
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-32646
- OSV: https://osv.dev/vulnerability/CVE-2024-32646

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-32646/
Summaries are generated and may contain mistakes; the official description above is the record.