How severe is GHSA-375m-5fvv-xq23?

No CVSS score has been assigned to GHSA-375m-5fvv-xq23 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-375m-5fvv-xq23?

GHSA-375m-5fvv-xq23 affects the following packages: vyper (PyPI). Ecosystems affected: PyPI.

How do I fix GHSA-375m-5fvv-xq23?

Update vyper to 0.2.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-375m-5fvv-xq23 is resolved across your whole dependency graph.

How do I detect GHSA-375m-5fvv-xq23 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vyper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-375m-5fvv-xq23 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-375m-5fvv-xq23 actively exploited in the wild?

No public exploit code has been indexed for GHSA-375m-5fvv-xq23 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-375m-5fvv-xq23 published, and has it been updated?

GHSA-375m-5fvv-xq23 was published on April 19, 2021 and was last updated on December 2, 2024. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

VVE-2021-0002: Incorrect `returndatasize` when using simple forwarder proxies deployed prior to EIP-1167 adoptionGHSA-375m-5fvv-xq23

Fix: vyperlang/vyper#2281

GHSA-375m-5fvv-xq23 is a security vulnerability in vyper. A fix is available for vyper — see the affected versions and patch details below.

Published

Apr 19, 2021

Updated

Dec 2, 2024

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Dec 2, 2024 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐍vyper

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Background

@tjayrush reported a data handling issue with certain Web3 libraries using Vyper-deploy forwarder proxy contracts using our Vyper's built-in create_forwarder_to function prior to our change to support EIP-1167 style forwarder proxies.

Impact

If you are an end user of a forwarder-style proxy deployed using Vyper's built-in create_forwarder_to function AND you have a function that returns >4096 bytes AND you do no return data sanitation on the value returned, you could potentially see a data corruption issue.

Otherwise, if you are handling the result of a return call AND you expect a specific RETURNDATASIZE that is less than 4096 (such as SafeERC20.safeTransfer) then the call will fail that check.

Patches

The issue was patched when we upgraded to EIP-1167 style forwarder proxies in #2281.

Workarounds

If you are making a call to a contract method that is expected to return <= 4096 bytes, there is no issue as the ABI decoders in both Solidity and Vyper will truncate the data properly. Web3 libraries will also do this, unless you are doing eth_call or eth_sendTransaction directly.

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`vyper`	all versions	0.2.9`pip install --upgrade 'vyper==0.2.9'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vyper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vyper to 0.2.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-375m-5fvv-xq23 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

## Background @tjayrush reported a data handling issue with certain Web3 libraries using Vyper-deploy forwarder proxy contracts using our Vyper's built-in `create_forwarder_to` function prior to our change to support EIP-1167 style forwarder proxies. ### Impact If you are an end user of a forwarder-style proxy deployed using Vyper's built-in `create_forwarder_to` function AND you have a function that returns >4096 bytes AND you do no return data sanitation on the value returned, you could potentially see a data corruption issue. Otherwise, if you are handling the result of a return call AND

O3 Security · Impact-Aware SCA

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