Multiple evaluation of contract address in call in vyperGHSA-4v9q-cgpw-cf38
HIGHFix: vyperlang/vyper@6b4d8ffGHSA-4v9q-cgpw-cf38 is a high-severity (CVSS 7.5) CWE-670 vulnerability in vyper. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for vyper — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-4v9q-cgpw-cf38.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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
Impact
when a calling an external contract with no return value, the contract address could be evaluated twice. this is usually only an efficiency problem, but if evaluation of the contract address has side effects, it could result in double evaluation of the side effects.
in the following example, Foo(msg.sender).bar() is the contract address for the following call (to .foo()), and could get evaluated twice
interface Foo:
def foo(): nonpayable
def bar() -> address: nonpayable
@external
def do_stuff():
Foo(Foo(msg.sender).bar()).foo()
Patches
6b4d8ff185de071252feaa1c319712b2d6577f8d
Workarounds
assign contract addresses to variables. the above example would change to
@external
def do_stuff():
t: Foo = Foo(msg.sender).bar()
t.foo()
References
For more information
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vyper | all versions | 0.3.4pip install --upgrade 'vyper==0.3.4' |
Affected Products
vypervyperlangResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & 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 0.3.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4v9q-cgpw-cf38 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
Is GHSA-4v9q-cgpw-cf38 in your dependencies?
Find it across PyPI, including transitive dependencies.