Summary
vyper performs multiple eval of sqrt() argument built in
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);
}
}
Impact
No vulnerable production contracts were found.
CVE-2024-32649 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.4.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Patched in https://github.com/vyperlang/vyper/pull/3976.
Frequently Asked Questions
- What is CVE-2024-32649? CVE-2024-32649 is a medium-severity security vulnerability in vyper (pip), affecting versions < 0.4.0. It is fixed in 0.4.0.
- How severe is CVE-2024-32649? CVE-2024-32649 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of vyper are affected by CVE-2024-32649? vyper (pip) versions < 0.4.0 is affected.
- Is there a fix for CVE-2024-32649? Yes. CVE-2024-32649 is fixed in 0.4.0. Upgrade to this version or later.
- Is CVE-2024-32649 exploitable, and should I be worried? Whether CVE-2024-32649 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2024-32649 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2024-32649? Upgrade
vyperto 0.4.0 or later.