What’s Vulnerable › Vulnerabilities

CVE-2021-48019: Vyper before 0.2.9 Incorrect RETURNDATASIZE in create_forwarder_to Proxies

• Severity: medium (CVSS 4.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-21 · updated 2026-10-27
• Weakness: CWE-805

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.

Affected products

• vyperlang vyper: before 0.2.9 — fixed in 0.2.9

How to fix

Upgrade to a fixed version: vyperlang vyper 0.2.9. Check the vendor advisory for mitigations.

References

• https://github.com/vyperlang/vyper/security/advisories/GHSA-375m-5fvv-xq23
• https://www.vulncheck.com/advisories/vyper-before-0.2.9-incorrect-returndatasize-in-create-forwarder-to-proxies

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