CVE-2020-35864: Flatbuffers Dangling Reference Vulnerability

HIGH
Advisory Identifier: GHSA-c9h5-hf8r-m97x
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CVSS 7.5
CWE-704
Published
Advisory Summary

CVE-2020-35864 is a HIGH (CVSS 7.5) dangling reference vulnerability (CWE-704: Incorrect Type Conversion or Cast) affecting Flatbuffers libraries in the crates.io ecosystem. The issue involves dangling reference in flatbuffers. Remediation is available by upgrading affected packages to version 2.0.0.

CVE-2020-35864 at a Glance

CVE Identifier CVE-2020-35864
GHSA Identifier GHSA-c9h5-hf8r-m97x
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-704: Incorrect Type Conversion or Cast
Affected Product Flatbuffers
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2020-35864

To remediate this vulnerability, upgrade all affected Flatbuffers dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

flatbuffers fixed: 2.0.0 
Upgrade flatbuffers to 2.0.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for flatbuffers

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-35864, inspect your project dependencies for Flatbuffers:

inspect dependencies for flatbuffers

Analyze the terminal output to locate any version of Flatbuffers in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.0.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-704: Incorrect Type Conversion or Cast, where the product does not correctly convert an object, resource, or structure from one type to a different type. In Flatbuffers, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

An issue was discovered in the flatbuffers crate through 2020-04-11 for Rust. read_scalar (and read_scalar_at) can transmute values without unsafe blocks.

CVE-2020-35864 Affected Flatbuffers Versions

1 component(s)
Fixed Versions:
2.0.0
Product / Package Ecosystem Affected Versions Fixed Version
flatbuffers
 crates.io
≥ 0.4.0
< 2.0.0
2.0.0

References

NVD — CVE-2020-35864 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-35864
Flatbuffers Source Repository REPOSITORY
https://github.com/google/flatbuffers/issues/5825
Flatbuffers Source Repository REPOSITORY
https://github.com/google/flatbuffers
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2020-0009.html

Frequently Asked Questions

What is CVE-2020-35864?
CVE-2020-35864 is a security vulnerability in Flatbuffers involving Dangling reference in flatbuffers under CWE-704: Incorrect Type Conversion or Cast.
Which Flatbuffers versions are affected?
Affected versions include releases prior to 2.0.0 across affected packages: flatbuffers.
What version fixes CVE-2020-35864?
Upgrading to 2.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is flatbuffers affected?
Yes, flatbuffers is affected in releases prior to 2.0.0. Upgrade your dependency to 2.0.0 or later.
What is the CVSS score of CVE-2020-35864?
CVE-2020-35864 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2020-35864?
CVE-2020-35864 is classified under CWE-704: Incorrect Type Conversion or Cast (The product does not correctly convert an object, resource, or structure from one type to a different type.).
How can I check crates.io dependencies for CVE-2020-35864?
Run the dependency tree command: 'inspect dependencies for flatbuffers'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c9h5-hf8r-m97x",
  "modified" : "2021-08-19T21:18:24Z",
  "published" : "2021-08-25T20:47:36Z",
  "aliases" : [ "CVE-2020-35864" ],
  "summary" : "Dangling reference in flatbuffers",
  "details" : "An issue was discovered in the flatbuffers crate through 2020-04-11 for Rust. read_scalar (and read_scalar_at) can transmute values without unsafe blocks.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "flatbuffers"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.4.0"
      }, {
        "fixed" : "2.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-35864"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/google/flatbuffers/issues/5825"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/google/flatbuffers"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2020-0009.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-704" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T21:18:24Z",
    "nvd_published_at" : null
  }
}