CVE-2024-32649 is a medium-severity (CVSS 5.3) CWE-95 vulnerability in vyper. A fix is available for vyper — see the affected versions and patch details below.
vyper performs double eval of the argument of sqrt
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 CVE-2024-32649.
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.
How urgent is this, really
CVE-2024-32649 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
Summary
Using the sqrt builtin can result in multiple eval evaluation of side effects when the argument has side-effects. The bug is more difficult (but not impossible!) to trigger as of 0.3.4, when the unique symbol fence was introduced (https://github.com/vyperlang/vyper/pull/2914).
A contract search was performed and no vulnerable contracts were found in production.
Details
It can be seen that the build_IR function of the sqrt builtin doesn't cache the argument to the stack:
https://github.com/vyperlang/vyper/blob/4595938734d9988f8e46e8df38049ae0559abedb/vyper/builtins/functions.py#L2151
As such, it can be evaluated multiple times (instead of retrieving the value from the stack).
PoC
With at least Vyper version 0.2.15+commit.6e7dba7 the following contract:
c: uint256
@internal
def some_decimal() -> decimal:
self.c += 1
return 1.0
@external
def foo() -> uint256:
k: decimal = sqrt(self.some_decimal())
return self.c
passes the following test:
// SPDX-License-Identifier: MIT
pragma solidity >=0.8.13;
import "../../lib/ds-test/test.sol";
import "../../lib/utils/Console.sol";
import "../../lib/utils/VyperDeployer.sol";
import "../ITest.sol";
contract ConTest is DSTest {
VyperDeployer vyperDeployer = new VyperDeployer();
ITest t;
function setUp() public {
t = ITest(vyperDeployer.deployContract("Test"));
}
function testFoo() public {
uint256 val = t.foo();
console.log(val);
assert (val == 4);
}
}
Patches
Patched in https://github.com/vyperlang/vyper/pull/3976.
Impact
No vulnerable production contracts were found.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | vyper | all versions | 0.4.0pip install --upgrade 'vyper==0.4.0' |
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 0.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-32649 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-32649 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-32649. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2024-32649 in your dependencies?
O3 Security finds CVE-2024-32649 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.