# CVE-2024-24560: Vyper external calls can overflow return data to return input buffer

> Attackers can exploit buffer overlap in Vyper external calls to read dirty input buffer data as return data, potentially leading to logic errors or code execution in smart contracts.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/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:** 2 Feb 2024
- **Updated:** 1 Aug 2024
- **Also known as:** GHSA-gp3w-2v2m-p686, PYSEC-2024-148

## What is CVE-2024-24560?

CVE-2024-24560 is a low-severity memory corruption vulnerability in vyperlang vyper, published on 2 Feb 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. When calls to external contracts are made, we write the input buffer starting at byte 28, and allocate the return buffer to start at byte 0 (overlapping with the input buffer). When checking RETURNDATASIZE for dynamic types, the size is compared only to the minimum allowed size for that type, and not to the returned value's length. As a result, malformed return data can cause the contract to mistake data from the input buffer for returndata.  When the called contract returns invalid ABIv2 encoded data, the calling contract can read different invalid data (from the dirty buffer) than the called contract returned.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2024-24560?

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 | 0.4.0b1 |

Products: Vyperlang Vyper.

## How do I fix CVE-2024-24560?

Upgrade vyper to a fixed version for your release line: 0.4.0 or 0.4.0b1.

## Is CVE-2024-24560 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-24560 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-2024-24560 and fix it if it is affected.

What it is: CVE-2024-24560 is a low-severity memory corruption vulnerability in vyperlang vyper, published on 2 Feb 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-2024-24560 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 0.4.0b1

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-2024-24560/ (Markdown: https://insights.sbomify.com/CVE-2024-24560/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-24560
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-24560
- OSV: https://osv.dev/vulnerability/CVE-2024-24560

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-24560/
Summaries are generated and may contain mistakes; the official description above is the record.