Vulnerability · Published Oct 21, 2026 · Assigned by VulnCheck
CVE-2020-37289Vyper before 0.3.1 Improper Input Validation of uint8 Interface Return Values
Low 3.7
In plain English
A low-severity improper input validation in vyper from vyperlang. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities).
Severity (CVSS 3.1)3.7Low
Exploit odds (30 days)0.3%top 82.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Vyper before 0.3.1 lacks a uint8 type, allowing interface return values declared as uint8, such as ERC20.decimals(), to be stored in uint256 variables without bounds checking. Malicious contracts can return values greater than 255 to manipulate or bypass contract logic that relies on these values.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | vyper | no fix listed | GHSA-mr6r-mvw4-736g |
Affected products (as reported)
Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
References
- GitHub Security Advisory (GHSA-mr6r-mvw4-736g) vendor-advisory
- VulnCheck Advisory: Vyper before 0.3.1 Improper Input Validation of uint8 Interface Return Values third-party-advisory