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.

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact Low

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Affected Vendors & Products

Vendors Products
Vyperlang Subscribe
Vyper Subscribe

No data.

No data.

No data.

Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/vyperlang/vyper/security/advisories/GHSA-mr6r-mvw4-736g cve-icon cve-icon
https://www.vulncheck.com/advisories/vyper-before-0.3.1-improper-input-validation-of-uint8-interface-return-values cve-icon cve-icon
History

Wed, 21 Oct 2026 00:45:00 +0000

Type Values Removed Values Added
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.
Title Vyper before 0.3.1 Improper Input Validation of uint8 Interface Return Values
First Time appeared Vyperlang
Vyperlang vyper
Weaknesses CWE-20
CPEs cpe:2.3:a:vyperlang:vyper:*:*:*:*:*:*:*:*
Vendors & Products Vyperlang
Vyperlang vyper
References
Metrics cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-21T00:36:17.573Z

Reserved: 2026-10-20T21:53:41.760Z

Link: CVE-2020-37289

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-21T01:17:18.830

Modified: 2026-10-21T01:17:18.830

Link: CVE-2020-37289

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses