RUSTSEC-2020-0009

read_scalar and read_scalar_at allow transmuting values without unsafe blocks

Reported

April 11, 2020

Issued

October 2, 2020 (last modified: October 19, 2021)

Package

flatbuffers (crates.io)

Type

Vulnerability

Aliases

CVE-2020-35864

Details

https://github.com/google/flatbuffers/issues/5825

CVSS Score

7.5 HIGH

CVSS Details

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Patched

>=2.0.0

Unaffected

<0.4.0

Affected Functions

Version

flatbuffers::read_scalar

>=0.4.0

flatbuffers::read_scalar_at

>=0.4.0

Description

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>()]));
}