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CVE-2021-48019 Details

ANALYZED

This CVE record has been analyzed and enriched by NVDAPI.com as an independent party.

Description

Vyper before 0.2.9 deploys forwarder proxies through the built-in create_forwarder_to function that report a fixed 4096-byte RETURNDATASIZE rather than the actual return data size. Calls through these proxies can yield corrupted data when a function returns more than 4096 bytes without return data sanitation, and fail strict return-size checks such as SafeERC20.safeTransfer.

Metrics

CVSS 3.x Severity and Vector Strings:

VolerionCVSS-B:6.5 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CNA: [email protected]CVSS-B:4.8 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/vyperlang/vyper/security/advisories/GHSA-375m-5fvv-xq23	[email protected]	AdvisoryRemedyVendor
https://www.vulncheck.com/advisories/vyper-before-0.2.9-incorrect-returndatasize-in-create-forwarder-to-proxies	[email protected]	Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-805	Buffer Access with Incorrect Length Value	[email protected]

Affected Products

Product	Versions
Vyper	< 0.2.9 (semver)
CPE cpe:2.3:a:vyper_project:vyper:::::::: Remediation Upgrade: 0.2.9moderate effort Mitigation:low effort If you are using a Solidity library that checks RETURNDATASIZE of an external call to a forwarder proxy deployed prior to this patch, it will fail on that assertion (such as SafeERC20.safeTransfer). The workaround is to always do a greater than or equal to check, rather than a strict equals to check.

Product

Versions

Vyper

< 0.2.9 (semver)

CPE

cpe:2.3:a:vyper_project:vyper:*:*:*:*:*:*:*:*

Remediation

Upgrade: 0.2.9moderate effort
Mitigation:low effort
If you are using a Solidity library that checks RETURNDATASIZE of an external call to a forwarder proxy deployed prior to this patch, it will fail on that assertion (such as SafeERC20.safeTransfer). The workaround is to always do a greater than or equal to check, rather than a strict equals to check.

Change History

2 change records found show changes

Date	Action	Recorded By
Oct 27, 2026	CVE Modified	CISA-ADP
Oct 21, 2026	New CVE Received	[email protected]