Improper Validation of Specified Quantity in Input Affecting vyper package, versions [,0.3.1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-VYPER-22132608
- published2 Nov 2026
- disclosed21 Oct 2026
- creditUnknown
Introduced: 21 Oct 2026
NewCVE-2020-37289 (opens in a new tab)How to fix?
Upgrade vyper to version 0.3.1 or higher.
Overview
vyper is a Pythonic Smart Contract Language for the EVM.
Affected versions of this package are vulnerable to Improper Validation of Specified Quantity in Input via the absence of a uint8 type, which causes interface return values declared as uint8 (such as ERC20.decimals()) to be stored into uint256 variables without bounds checking. Because the ABI encodes uint8 return values as 32-byte integers, a malicious contract can return a value greater than 255, allowing an attacker to manipulate or bypass contract logic that relies on the assumption that the value is within the uint8 range.
Workaround
Insert an explicit bounds assertion after reading any interface value declared as uint8, for example: assert decimals < 256.