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

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-04-25 · updated 2026-06-17
Weakness: CWE-20

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.

Affected products

vyperlang vyper: before 0.4.0 — fixed in 0.4.0

How to fix

Upgrade to a fixed version: vyperlang vyper 0.4.0. Check the vendor advisory for mitigations.

References

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