GHSA-g2xh-c426-v8mf
MEDIUMVyper: reversed order of side effects for some operations
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
For the following (probably non-exhaustive) list of expressions, the compiler evaluates the arguments from right to left instead of left to right.
- unsafe_add
- unsafe_sub
- unsafe_mul
- unsafe_div
- pow_mod256
- |, &, ^ (bitwise operators)
- bitwise_or (deprecated)
- bitwise_and (deprecated)
- bitwise_xor (deprecated)
- raw_call
- <, >, <=, >=, ==, !=
- in, not in (when lhs and rhs are enums)
This behaviour becomes a problem when the evaluation of one of the arguments produces side effects that other arguments depend on. The following expressions can produce side-effect:
- state modifying external call
- state modifying internal call
raw_callpop()when used on a Dynamic Array stored in the storagecreate_minimal_proxy_tocreate_copy_ofcreate_from_blueprint
For example:
f:uint256
@internal
def side_effect() -> uint256:
self.f = 12
return 1
@external
def foo() -> uint256:
return unsafe_add(self.f,self.side_effect()) # returns 13 instead of 1
a:DynArray[uint256, 12]
@external
def bar() -> bool:
self.a = [1,2,3]
return len(self.a) == self.a.pop() # return false instead of true
Patches
not yet patched, will address in a future release. tracking in https://github.com/vyperlang/vyper/issues/3604.
Workarounds
When using expressions from the list above, make sure that the arguments of the expression do not produce side effects or, if one does, that no other argument is dependent on those side effects.
References
Are there any links users can visit to find out more?
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vyper | all versions | No fix |
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.
Remediation status
No patched version of vyper has shipped for GHSA-g2xh-c426-v8mf yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-g2xh-c426-v8mf 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-g2xh-c426-v8mf. 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-g2xh-c426-v8mf in your dependencies?
O3 detects GHSA-g2xh-c426-v8mf across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.