ghsa-5jrj-52x8-m64h
Vulnerability from github
Published
2024-04-25 19:50
Modified
2025-01-21 17:53
Severity ?
5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Summary
vyper performs multiple eval of `sqrt()` argument built in
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.

Show details on source website

To clipboard 

{
   affected: [
      {
         package: {
            ecosystem: "PyPI",
            name: "vyper",
         },
         ranges: [
            {
               events: [
                  {
                     introduced: "0",
                  },
                  {
                     fixed: "0.4.0",
                  },
               ],
               type: "ECOSYSTEM",
            },
         ],
      },
   ],
   aliases: [
      "CVE-2024-32649",
   ],
   database_specific: {
      cwe_ids: [
         "CWE-95",
      ],
      github_reviewed: true,
      github_reviewed_at: "2024-04-25T19:50:16Z",
      nvd_published_at: "2024-04-25T18:15:09Z",
      severity: "MODERATE",
   },
   details: "### Summary\nUsing 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).\n\nA contract search was performed and no vulnerable contracts were found in production.\n\n### Details\nIt can be seen that the `build_IR` function of the `sqrt` builtin doesn't cache the argument to the stack: \nhttps://github.com/vyperlang/vyper/blob/4595938734d9988f8e46e8df38049ae0559abedb/vyper/builtins/functions.py#L2151\n\nAs such, it can be evaluated multiple times (instead of retrieving the value from the stack).\n\n### PoC\nWith at least Vyper version `0.2.15+commit.6e7dba7` the following contract:\n```vyper\nc: uint256\n\n@internal\ndef some_decimal() -> decimal:\n    self.c += 1\n    return 1.0\n\n@external\ndef foo() -> uint256:\n    k: decimal = sqrt(self.some_decimal())\n    return self.c\n```\npasses the following test:\n```solidity\n// SPDX-License-Identifier: MIT\npragma solidity >=0.8.13;\n\nimport \"../../lib/ds-test/test.sol\";\nimport \"../../lib/utils/Console.sol\";\nimport \"../../lib/utils/VyperDeployer.sol\";\n\nimport \"../ITest.sol\";\n\ncontract ConTest is DSTest {\n    VyperDeployer vyperDeployer = new VyperDeployer();\n\n    ITest t;\n\n    function setUp() public {\n        t = ITest(vyperDeployer.deployContract(\"Test\"));\n    }\n\n    function testFoo() public {\n        uint256 val = t.foo();\n        console.log(val);\n        assert (val == 4);\n    }\n}\n```\n \n### Patches\nPatched in https://github.com/vyperlang/vyper/pull/3976.\n\n### Impact\nNo vulnerable production contracts were found.",
   id: "GHSA-5jrj-52x8-m64h",
   modified: "2025-01-21T17:53:44Z",
   published: "2024-04-25T19:50:16Z",
   references: [
      {
         type: "WEB",
         url: "https://github.com/vyperlang/vyper/security/advisories/GHSA-5jrj-52x8-m64h",
      },
      {
         type: "ADVISORY",
         url: "https://nvd.nist.gov/vuln/detail/CVE-2024-32649",
      },
      {
         type: "WEB",
         url: "https://github.com/vyperlang/vyper/pull/2914",
      },
      {
         type: "WEB",
         url: "https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2024-209.yaml",
      },
      {
         type: "PACKAGE",
         url: "https://github.com/vyperlang/vyper",
      },
   ],
   schema_version: "1.4.0",
   severity: [
      {
         score: "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
         type: "CVSS_V3",
      },
   ],
   summary: "vyper performs multiple eval of `sqrt()` argument built in",
}


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