CVE-2020-35903: Dync Out Of Bounds Read Vulnerability

MODERATE
Advisory Identifier: GHSA-qxjq-v4wf-ppvh
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CVSS 5.5
CWE-125
Published
Advisory Summary

CVE-2020-35903 is a MODERATE (CVSS 5.5) out of bounds read vulnerability (CWE-125: Out-of-bounds Read) affecting Dync libraries in the crates.io ecosystem. The issue involves out of bounds read in dync. Remediation is available by upgrading affected packages to version 0.5.0.

CVE-2020-35903 at a Glance

CVE Identifier CVE-2020-35903
GHSA Identifier GHSA-qxjq-v4wf-ppvh
Severity MODERATE
CVSS v3.1 Base Score 5.5
CWE Classification CWE-125: Out-of-bounds Read
Affected Product Dync
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 5.5

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

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
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-2020-35903

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

dync fixed: 0.5.0 
Upgrade dync to 0.5.0
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 dync

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-35903, inspect your project dependencies for Dync:

inspect dependencies for dync

Analyze the terminal output to locate any version of Dync in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.5.0), 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-125: Out-of-bounds Read, where the product reads data past the end, or before the beginning, of the intended buffer. In Dync, 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

VecCopy::data is created as a Vec of u8 but can be used to store and retrieve elements of different types leading to misaligned access. The issue was resolved in v0.5.0 by replacing data being stored by Vec<u8> with a custom managed pointer. Elements are now stored and retrieved using types with proper alignment corresponding to original types.

CVE-2020-35903 Affected Dync Versions

1 component(s)
Fixed Versions:
0.5.0
Product / Package Ecosystem Affected Versions Fixed Version
dync
 crates.io
< 0.5.0
0.5.0

References

NVD — CVE-2020-35903 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-35903
Dync Source Repository REPOSITORY
https://github.com/elrnv/dync/issues/4
Dync Source Repository REPOSITORY
https://github.com/elrnv/dync
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2020-0050.html

Frequently Asked Questions

What is CVE-2020-35903?
CVE-2020-35903 is a security vulnerability in Dync involving Out of bounds read in dync under CWE-125: Out-of-bounds Read.
Which Dync versions are affected?
Affected versions include releases prior to 0.5.0 across affected packages: dync.
What version fixes CVE-2020-35903?
Upgrading to 0.5.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is dync affected?
Yes, dync is affected in releases prior to 0.5.0. Upgrade your dependency to 0.5.0 or later.
What is the CVSS score of CVE-2020-35903?
CVE-2020-35903 has a CVSS v3.1 base score of 5.5 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2020-35903?
CVE-2020-35903 is classified under CWE-125: Out-of-bounds Read (The product reads data past the end, or before the beginning, of the intended buffer.).
How can I check crates.io dependencies for CVE-2020-35903?
Run the dependency tree command: 'inspect dependencies for dync'. 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-qxjq-v4wf-ppvh",
  "modified" : "2023-06-13T17:12:14Z",
  "published" : "2021-08-25T20:49:47Z",
  "aliases" : [ "CVE-2020-35903" ],
  "summary" : "Out of bounds read in dync",
  "details" : "VecCopy::data is created as a Vec of u8 but can be used to store and retrieve elements of different types leading to misaligned access.\n\nThe issue was resolved in v0.5.0 by replacing data being stored by Vec<u8> with a custom managed pointer. Elements are now stored and retrieved using types with proper alignment corresponding to original types.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "dync"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.5.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-35903"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/elrnv/dync/issues/4"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/elrnv/dync"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2020-0050.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-125" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T20:50:45Z",
    "nvd_published_at" : "2020-12-31T09:15:00Z"
  }
}