CVE-2020-35865: Os str bytes :from_u32_unchecked` Vulnerability

HIGH
Advisory Identifier: GHSA-q948-x8rf-888m
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CVSS 7.5
CWE-704
Published
Advisory Summary

CVE-2020-35865 is a HIGH (CVSS 7.5) :from_u32_unchecked` vulnerability (CWE-704: Incorrect Type Conversion or Cast) affecting Os str bytes libraries in the crates.io ecosystem. The issue involves :from_u32_unchecked`. Remediation is available by upgrading affected packages to version 2.0.0.

CVE-2020-35865 at a Glance

CVE Identifier CVE-2020-35865
GHSA Identifier GHSA-q948-x8rf-888m
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-704: Incorrect Type Conversion or Cast
Affected Product Os str bytes
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-2020-35865

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

os_str_bytes fixed: 2.0.0 
Upgrade os_str_bytes 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 os_str_bytes

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-35865, inspect your project dependencies for Os str bytes:

inspect dependencies for os_str_bytes

Analyze the terminal output to locate any version of Os str bytes 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 Os str bytes, 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

The Windows implementation of this crate relied on the behavior of std::char::from_u32_unchecked when its safety clause is violated. Even though this worked with Rust versions up to 1.42 (at least), that behavior could change with any new Rust version, possibly leading a security issue. The flaw was corrected in version 2.0.0.

CVE-2020-35865 Affected Os str bytes Versions

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

References

NVD — CVE-2020-35865 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-35865
Os str bytes Source Repository REPOSITORY
https://github.com/dylni/os_str_bytes/pull/1
Os str bytes Source Repository REPOSITORY
https://github.com/dylni/os_str_bytes
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2020-0012.html

Frequently Asked Questions

What is CVE-2020-35865?
CVE-2020-35865 is a security vulnerability in Os str bytes involving :from_u32_unchecked` under CWE-704: Incorrect Type Conversion or Cast.
Which Os str bytes versions are affected?
Affected versions include releases prior to 2.0.0 across affected packages: os_str_bytes.
What version fixes CVE-2020-35865?
Upgrading to 2.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is os_str_bytes affected?
Yes, os_str_bytes 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-2020-35865?
CVE-2020-35865 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-2020-35865?
CVE-2020-35865 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-2020-35865?
Run the dependency tree command: 'inspect dependencies for os_str_bytes'. 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-q948-x8rf-888m",
  "modified" : "2023-06-13T20:12:22Z",
  "published" : "2021-08-25T20:47:55Z",
  "aliases" : [ "CVE-2020-35865" ],
  "summary" : "os_str_bytes relies on undefined behavior of `char::from_u32_unchecked`",
  "details" : "The Windows implementation of this crate relied on the behavior of std::char::from_u32_unchecked when its safety clause is violated. Even though this worked with Rust versions up to 1.42 (at least), that behavior could change with any new Rust version, possibly leading a security issue.\n\nThe flaw was corrected in version 2.0.0.",
  "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" : "os_str_bytes"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-35865"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/dylni/os_str_bytes/pull/1"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/dylni/os_str_bytes"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2020-0012.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-704" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T21:08:17Z",
    "nvd_published_at" : "2020-12-31T10:15:00Z"
  }
}