CVE-2023-32675: Nonpayable default functions are sometimes payable in vyper
First published: Fri May 19 2023(Updated: )
### Impact in contracts with at least one regular nonpayable function, due to the callvalue check being inside of the selector section, it is possible to send funds to the default function by using less than 4 bytes of calldata, even if the default function is marked `nonpayable`. this applies to contracts compiled with vyper<=0.3.7. ```vyper # @version 0.3.7 # implicitly nonpayable @external def foo() -> uint256: return 1 # implicitly nonpayable @external def __default__(): # could receive ether here pass ``` ### Patches this was fixed by the removal of the global calldatasize check in https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520. ### Workarounds don't use nonpayable default functions
Credit: security-advisories@github.com security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/vyper | <0.3.8 | 0.3.8 |
| Vyperlang Vyper | <0.3.8 |
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Reference Links
- https://github.com/vyperlang/vyper/security/advisories/GHSA-vxmm-cwh2-q762
- https://nvd.nist.gov/vuln/detail/CVE-2023-32675
- https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520
- https://github.com/vyperlang/vyper/commit/903727006c1e5ebef99fa9fd5d51d62bd33d72a9
- https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2023-80.yaml
- https://github.com/advisories/GHSA-vxmm-cwh2-q762 (Advisory)
- https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520.
Frequently Asked Questions
What is CVE-2023-32675?
CVE-2023-32675 is a vulnerability in the Vyper smart contract language for the Ethereum virtual machine.
How does CVE-2023-32675 affect Vyper?
CVE-2023-32675 allows funds to be sent to the default function of contracts with multiple regular nonpayable functions, even if the default function is marked nonpayable.
Which versions of Vyper are affected by CVE-2023-32675?
Vyper versions up to and excluding 0.3.8 are affected by CVE-2023-32675.
What is the severity of CVE-2023-32675?
CVE-2023-32675 has a severity rating of medium (5.3).
How can I fix CVE-2023-32675?
To fix CVE-2023-32675, update Vyper to a version that is equal to or greater than 0.3.8.
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