ghsa-ppx5-q359-pvwj
Vulnerability from github
Published
2024-04-25 19:53
Modified
2024-04-25 19:53
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's range(start, start + N) reverts for negative numbers
Details

Summary

When looping over a range of the form range(start, start + N), if start is negative, the execution will always revert.

Details

This issue is caused by an incorrect assertion inserted by the code generation of the range (stmt.parse_For_range()):

https://github.com/vyperlang/vyper/blob/9136169468f317a53b4e7448389aa315f90b95ba/vyper/codegen/stmt.py#L286-L287

This assertion was introduced in https://github.com/vyperlang/vyper/commit/3de1415ee77a9244eb04bdb695e249d3ec9ed868 to fix https://github.com/advisories/GHSA-6r8q-pfpv-7cgj. The issue arises when start is signed, instead of using sle, le is used and start is interpreted as an unsigned integer for the comparison. If it is a negative number, its 255th bit is set to 1 and is hence interpreted as a very large unsigned integer making the assertion always fail.

PoC

Vyper @external def foo(): x:int256 = min_value(int256) # revert when it should not since we have the following assertion that fails: # [assert, [le, min_value(int256), max_value(int256) + 1 - 10]], for i in range(x, x + 10): pass

Patches

patched in v0.4.0, specifically, https://github.com/vyperlang/vyper/pull/3679 disallows this form of range().

Impact

Any contract having a range(start, start + N) where start is a signed integer with the possibility for start to be negative is affected. If a call goes through the loop while supplying a negative start the execution will revert.

Show details on source website

To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "vyper"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.3.8"
            },
            {
              "fixed": "0.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-32481"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-681"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-04-25T19:53:43Z",
    "nvd_published_at": "2024-04-25T17:15:50Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nWhen looping over a `range` of the form `range(start, start + N)`, if `start` is negative, the execution will always revert.\n \n### Details\n\nThis issue is caused by an incorrect assertion inserted by the code generation of the range (`stmt.parse_For_range()`):\n\nhttps://github.com/vyperlang/vyper/blob/9136169468f317a53b4e7448389aa315f90b95ba/vyper/codegen/stmt.py#L286-L287\n\nThis assertion was introduced in https://github.com/vyperlang/vyper/commit/3de1415ee77a9244eb04bdb695e249d3ec9ed868 to fix https://github.com/advisories/GHSA-6r8q-pfpv-7cgj. The issue arises when `start` is signed, instead of using `sle`, `le` is used and `start` is interpreted as an unsigned integer for the comparison. If it is a negative number, its 255th bit is set to `1` and is hence interpreted as a very large unsigned integer making the assertion always fail. \n### PoC\n\n```Vyper\n@external\ndef foo():\n    x:int256 = min_value(int256)\n    # revert when it should not since we have the following assertion that fails:\n    # [assert, [le, min_value(int256), max_value(int256) + 1 - 10]],\n    for i in range(x, x + 10):\n        pass\n```\n\n### Patches\n\npatched in v0.4.0, specifically, https://github.com/vyperlang/vyper/pull/3679 disallows this form of `range()`.\n\n### Impact\n\nAny contract having a `range(start, start + N)` where `start` is a signed integer with the possibility for `start` to be negative is affected. If a call goes through the loop while supplying a negative `start` the execution will revert.",
  "id": "GHSA-ppx5-q359-pvwj",
  "modified": "2024-04-25T19:53:43Z",
  "published": "2024-04-25T19:53:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/security/advisories/GHSA-ppx5-q359-pvwj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-32481"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/commit/3de1415ee77a9244eb04bdb695e249d3ec9ed868"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/commit/5319cfbe14951e007ccdb323257e5ada869b35d5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/vyperlang/vyper"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/blob/9136169468f317a53b4e7448389aa315f90b95ba/vyper/codegen/stmt.py#L286-L287"
    }
  ],
  "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\u0027s range(start, start + N) reverts for negative numbers"
}


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