CVE-2023-30629 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.
Vyper's raw_call with outsize=0 and revert_on_failure=False returns incorrect success value
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-30629.
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
Background
During the audit of Lido's Gate Seals code statemind team identified a weird behavior of the code that uses raw_call: https://github.com/lidofinance/gate-seals/blob/051593e74df01a4131c485b4fda52e691cd4b7d8/contracts/GateSeal.vy#L164 .
Construction like this:
success = raw_call(
sealable,
_abi_encode(SEAL_DURATION_SECONDS, method_id=method_id("pauseFor(uint256)")),
revert_on_failure=False
)
was not fully documented: https://docs.vyperlang.org/en/v0.3.7/built-in-functions.html#raw_call .
The documentation says that: if max_outsize=0 it should return nothing and then it says that if revert_on_failure=False it should return a success flag in the tuple of response, but what if max_outsize=0 and revert_on_failure=False.
So the team started researching what exactly happened in that case, after some research we found that the Vyper compiler generates the wrong bytecode in that case, it generates the sequence:
CALL // call
MLOAD // MLOAD is wrong since the CALL result is already stored in the stack
Impact
Example of buggy code:
@external
def returnSome(calling: address, a: uint256) -> bool:
success: bool = false
success = raw_call(
calling,
_abi_encode(a, method_id=method_id("a(uint256)")),
revert_on_failure=False
)
any contract that uses the raw_call with revert_on_failure=False and max_outsize=0 receives the wrong response from raw_call. Depending on the memory garbage, the result can be either True or False.
Patches
Fix by @charles-cooper https://github.com/vyperlang/vyper/commit/851f7a1b3aa2a36fd041e3d0ed38f9355a58c8ae
Workarounds
The simple workaround is always to put max_outsize>0.
Workaround example https://github.com/lidofinance/gate-seals/pull/5/files
References
Lido's fix: https://github.com/lidofinance/gate-seals/pull/5/files
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vyper | ≥ 0.3.1&&< 0.3.8 | 0.3.8pip install --upgrade 'vyper==0.3.8' |
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 0.3.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-30629 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 CVE-2023-30629 in your dependencies?
Find it across PyPI, including transitive dependencies.