GHSA-9P8R-4XP4-GW5W

Vulnerability from github – Published: 2024-02-26 20:11 – Updated: 2025-01-17 15:54
VLAI
Summary
Vyper's `_abi_decode` vulnerable to Memory Overflow
Details

Summary

If an excessively large value is specified as the starting index for an array in _abi_decode, it can cause the read position to overflow. This results in the decoding of values outside the intended array bounds, potentially leading to bugs in contracts that use arrays within _abi_decode. The advisory has been assigned low severity, because it is only observable if there is a memory write between two invocations of abi_decode on the same input.

Proof of Concept

event Pwn:
    pass

@external
def f(x: Bytes[32 * 3]):
    a: Bytes[32] = b"foo"
    y: Bytes[32 * 3] = x

    decoded_y1: Bytes[32] = _abi_decode(y, Bytes[32])
    a = b"bar"
    decoded_y2: Bytes[32] = _abi_decode(y, Bytes[32])

    if decoded_y1 != decoded_y2:
        log Pwn()

Sending the following calldata results in Pwn being emitted. 

0xd45754f8
0000000000000000000000000000000000000000000000000000000000000020
0000000000000000000000000000000000000000000000000000000000000060
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffa0

Patches

Patched in https://github.com/vyperlang/vyper/pull/3925, https://github.com/vyperlang/vyper/pull/4091, https://github.com/vyperlang/vyper/pull/4144, https://github.com/vyperlang/vyper/pull/4060.

Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
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-2024-26149"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-119",
      "CWE-120"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-02-26T20:11:07Z",
    "nvd_published_at": "2024-02-26T20:19:05Z",
    "severity": "LOW"
  },
  "details": "## Summary\n\nIf an excessively large value is specified as the starting index for an array in `_abi_decode`, it can cause the read position to overflow. This results in the decoding of values outside the intended array bounds, potentially leading to bugs in contracts that use arrays within `_abi_decode`. The advisory has been assigned low severity, because it is only observable if there is a memory write between two invocations of `abi_decode` on the same input.\n\n## Proof of Concept\n\n```vyper\nevent Pwn:\n    pass\n\n@external\ndef f(x: Bytes[32 * 3]):\n    a: Bytes[32] = b\"foo\"\n    y: Bytes[32 * 3] = x\n\n    decoded_y1: Bytes[32] = _abi_decode(y, Bytes[32])\n    a = b\"bar\"\n    decoded_y2: Bytes[32] = _abi_decode(y, Bytes[32])\n\n    if decoded_y1 != decoded_y2:\n        log Pwn()\n```\n\nSending the following calldata results in `Pwn` being emitted. \n\n```\n0xd45754f8\n0000000000000000000000000000000000000000000000000000000000000020\n0000000000000000000000000000000000000000000000000000000000000060\nffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffa0\n```\n\n### Patches\nPatched in https://github.com/vyperlang/vyper/pull/3925, https://github.com/vyperlang/vyper/pull/4091, https://github.com/vyperlang/vyper/pull/4144, https://github.com/vyperlang/vyper/pull/4060.",
  "id": "GHSA-9p8r-4xp4-gw5w",
  "modified": "2025-01-17T15:54:37Z",
  "published": "2024-02-26T20:11:07Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/security/advisories/GHSA-9p8r-4xp4-gw5w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26149"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/pull/3925"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/pull/4060"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/pull/4091"
    },
    {
      "type": "WEB",
      "url": "https://github.com/vyperlang/vyper/pull/4144"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/vyper/PYSEC-2024-164.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/vyperlang/vyper"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Vyper\u0027s `_abi_decode` vulnerable to Memory Overflow"
}



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