GHSA-3p37-3636-q8wv
HIGHVyper vulnerable to OOB DynArray access when array is on both LHS and RHS of an assignment
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
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
during codegen, the length word of a dynarray is written before the data, which can result in OOB array access in the case where the dynarray is on both the lhs and rhs of an assignment. here is a minimal example producing the issue:
a:DynArray[uint256,3]
@external
def test() -> DynArray[uint256,3]:
self.a = [1,2,3]
self.a = empty(DynArray[uint256,3])
self.a = [self.a[0],self.a[1],self.a[2]]
return self.a # return [1,2,3]
and here is an example demonstrating the issue can cause data corruption across call frames:
@external
def test() -> DynArray[uint256,3]:
self.a()
return self.b() # return [1,2,3]
@internal
def a():
a: uint256 = 0
b: uint256 = 1
c: uint256 = 2
d: uint256 = 3
@internal
def b() -> DynArray[uint256,3]:
a: DynArray[uint256,3] = empty(DynArray[uint256,3])
a = [a[0],a[1],a[2]]
return a
examples involving append and pop:
@internal
def foo():
c: DynArray[uint256, 1] = []
c.append(c[0])
@internal
def foo():
c: DynArray[uint256, 1] = [1]
c[0] = c.pop()
the expected behavior in all of the above cases is to revert due to oob array access.
Patches
patched in 4f8289a81206f767df1900ac48f485d90fc87edb
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
References
Are there any links users can visit to find out more?
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vyper | all versions | 0.3.8 |
Research 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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update vyper to 0.3.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3p37-3636-q8wv 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.
How O3 protects you
O3 pinpoints whether GHSA-3p37-3636-q8wv is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-3p37-3636-q8wv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-3p37-3636-q8wv in your dependencies?
O3 detects GHSA-3p37-3636-q8wv across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.