# CVE-2023-42460: Vyper's `_abi_decode` input not validated in complex expressions

Source: https://junglewise.ai/threats/cve-2023-42460-vyper-s-abi-decode-input-not-validated-in-complex-expressions  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2023-09-27  
License: CC BY 4.0 with a link back

CVE-2023-42460 · Severity: low · CVSS 3.1 · Published 2023-09-27

Vyper is a Pythonic Smart Contract Language for the EVM. The `_abi_decode()` function does not validate input when it is nested in an expression. Uses of `_abi_decode()` can be constructed which allow for bounds checking to be bypassed resulting in incorrect results. This issue has not yet been fixed, but a fix is expected in release `0.3.10`. Users are advised to reference pull request #3626.

Technologies: [vyper (PyPI)](https://junglewise.ai/threats/technologies/vyper). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2023-42460 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2023-42460 being exploited in the wild.

**How severe is CVE-2023-42460?** Low severity, with a CVSS score of 3.1, published 27 September 2023.

**Which products and versions are affected?** vyper (PyPI) ECOSYSTEM:introduced=0.3.4,fixed=0.3.10.

**Is there a fix for CVE-2023-42460?** Yes. vyper (PyPI): upgrade to 0.3.10 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2023-42460?** Check whether you run vyper (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- vyper (PyPI): upgrade to 0.3.10 or later

  ```sh
  pip install "vyper>=0.3.10"
  ```


## Affected products

- vyper (PyPI) ECOSYSTEM:introduced=0.3.4,fixed=0.3.10

## Identifiers

- CVE-2023-42460
- GHSA-cx2q-hfxr-rj97
- PYSEC-2023-191

## Related threats

- [Vyper memory corruption in nested function calls and tuples](https://junglewise.ai/threats/vyper-memory-corruption-using-function-calls-within-tuples-nested-calls-c0689acb)
- [Vyper stack corruption in complex type argument passing](https://junglewise.ai/threats/vyper-call-stack-corruption-when-passing-complex-type-containing-non-3deb0c30)
- [Vyper return statement in nested for loops causes revert](https://junglewise.ai/threats/vyper-return-inside-for-loop-more-than-1-level-deep-ee8a193d)
- [PYSEC-2026-2028 - Vyper's `slice()` may elide side-effects when output length is 0](https://junglewise.ai/threats/cve-2025-47774-vyper-s-slice-may-elide-side-effects-when-output-length-is-0)
- [PYSEC-2026-2029 - Vyper's `concat()` builtin may elide side-effects for zero-length arguments](https://junglewise.ai/threats/cve-2025-47285-vyper-s-concat-builtin-may-elide-side-effects-for-zero-length)