Summary
Vyper's nonpayable default functions are sometimes payable
Workarounds
don't use nonpayable default functions
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.
# @version 0.3.7
# implicitly nonpayable
@external
def foo() -> uint256:
return 1
# implicitly nonpayable
@external
def __default__():
# could receive ether here
pass
CVE-2023-32675 has a CVSS score of 3.7 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.3.8); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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this was fixed by the removal of the global calldatasize check in https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520.
Frequently Asked Questions
- What is CVE-2023-32675? CVE-2023-32675 is a medium-severity security vulnerability in vyper (pip), affecting versions < 0.3.8. It is fixed in 0.3.8.
- How severe is CVE-2023-32675? CVE-2023-32675 has a CVSS score of 3.7 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of vyper are affected by CVE-2023-32675? vyper (pip) versions < 0.3.8 is affected.
- Is there a fix for CVE-2023-32675? Yes. CVE-2023-32675 is fixed in 0.3.8. Upgrade to this version or later.
- Is CVE-2023-32675 exploitable, and should I be worried? Whether CVE-2023-32675 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-32675 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-32675? Upgrade
vyperto 0.3.8 or later.