rustsec-2020-0009
Vulnerability from osv_rustsec
Published
2020-04-11 12:00
Modified
2023-06-13 13:10
Summary
`read_scalar` and `read_scalar_at` allow transmuting values without `unsafe` blocks
Details

The read_scalar and read_scalar_at functions are unsound because they allow transmuting values without unsafe blocks.

The following example shows how to create a dangling reference:

fn main() {
    #[derive(Copy, Clone, PartialEq, Debug)]
    struct S(&'static str);
    impl flatbuffers::EndianScalar for S {
        fn to_little_endian(self) -> Self { self }
        fn from_little_endian(self) -> Self { self }
    }
    println!("{:?}", flatbuffers::read_scalar::<S>(&[1; std::mem::size_of::<S>()]));
}
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "categories": [],
        "cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [
            "flatbuffers::read_scalar",
            "flatbuffers::read_scalar_at"
          ],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "flatbuffers",
        "purl": "pkg:cargo/flatbuffers"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.4.0"
            },
            {
              "fixed": "2.0.0"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [
    "CVE-2020-35864",
    "GHSA-c9h5-hf8r-m97x"
  ],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "The `read_scalar` and `read_scalar_at` functions are unsound\nbecause they allow transmuting values without `unsafe` blocks.\n\nThe following example shows how to create a dangling reference:\n\n```\nfn main() {\n    #[derive(Copy, Clone, PartialEq, Debug)]\n    struct S(\u0026\u0027static str);\n    impl flatbuffers::EndianScalar for S {\n        fn to_little_endian(self) -\u003e Self { self }\n        fn from_little_endian(self) -\u003e Self { self }\n    }\n    println!(\"{:?}\", flatbuffers::read_scalar::\u003cS\u003e(\u0026[1; std::mem::size_of::\u003cS\u003e()]));\n}\n```",
  "id": "RUSTSEC-2020-0009",
  "modified": "2023-06-13T13:10:24Z",
  "published": "2020-04-11T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/flatbuffers"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2020-0009.html"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/google/flatbuffers/issues/5825"
    }
  ],
  "related": [],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "`read_scalar` and `read_scalar_at` allow transmuting values without `unsafe` blocks"
}


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