CVE-2021-41121 is a high-severity (CVSS 8.8) Buffer Overflow vulnerability in vyper. A fix is available for vyper — see the affected versions and patch details below.
Memory corruption when returning a literal struct with a private call inside of it
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-41121 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
vyperReal-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
Vyper is a Pythonic Smart Contract Language for the EVM. In affected versions when performing a function call inside a literal struct, there is a memory corruption issue that occurs because of an incorrect pointer to the the top of the stack. This issue has been resolved in version 0.3.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vyper | all versions | 0.3.0pip install --upgrade 'vyper==0.3.0' |
Affected Products
vypervyperlangDetection & mitigation playbook
Open-source dependencyDetect
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 0.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41121 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Frequently Asked Questions
Is CVE-2021-41121 in your dependencies?
Find it across PyPI, including transitive dependencies.