Loading HuntDB...

GHSA-5jrj-52x8-m64h

GitHub Security Advisory

vyper performs multiple eval of `sqrt()` argument built in

✓ GitHub Reviewed MODERATE Has CVE

Advisory Details

### 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:
```vyper
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:
```solidity
// 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

PyPI vyper
Affected versions: 0 (fixed in 0.4.0)

Related CVEs

Key Information

GHSA ID
GHSA-5jrj-52x8-m64h
Published
April 25, 2024 7:50 PM
Last Modified
January 21, 2025 5:53 PM
CVSS Score
5.0 /10
Primary Ecosystem
PyPI
Primary Package
vyper
GitHub Reviewed
✓ Yes

Dataset

Last updated: June 18, 2025 6:25 AM

Data from GitHub Advisory Database. This information is provided for research and educational purposes.