CVE-2018-20996: Crossbeam Double Free Vulnerability

CRITICAL
Advisory Identifier: GHSA-c3cw-c387-pj65
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CVSS 9.8
CWE-415
Published
Advisory Summary

CVE-2018-20996 is a CRITICAL (CVSS 9.8) double free vulnerability (CWE-415: Double Free) affecting Crossbeam libraries in the crates.io ecosystem. The issue involves double free in crossbeam. Remediation is available by upgrading affected packages to version 0.4.1.

CVE-2018-20996 at a Glance

CVE Identifier CVE-2018-20996
GHSA Identifier GHSA-c3cw-c387-pj65
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-415: Double Free
Affected Product Crossbeam
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2018-20996

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

crossbeam fixed: 0.4.1 
Upgrade crossbeam to 0.4.1
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 crossbeam

How to Check if You Are Affected

To determine whether your application is affected by CVE-2018-20996, inspect your project dependencies for Crossbeam:

inspect dependencies for crossbeam

Analyze the terminal output to locate any version of Crossbeam in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.4.1), 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-415: Double Free, where the product calls free() twice on the same memory address. In Crossbeam, 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

Even if an element is popped from a queue, crossbeam would run its destructor inside the epoch-based garbage collector. This is a source of double frees. The flaw was corrected by wrapping elements inside queues in a ManuallyDrop.

CVE-2018-20996 Affected Crossbeam Versions

1 component(s)
Fixed Versions:
0.4.1
Product / Package Ecosystem Affected Versions Fixed Version
crossbeam
 crates.io
≥ 0.4.0
< 0.4.1
0.4.1

References

NVD — CVE-2018-20996 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-20996
Crossbeam Source Repository REPOSITORY
https://github.com/crossbeam-rs/crossbeam-epoch/issues/82
Crossbeam Source Repository REPOSITORY
https://github.com/crossbeam-rs/crossbeam-epoch
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2018-0009.html

Frequently Asked Questions

What is CVE-2018-20996?
CVE-2018-20996 is a security vulnerability in Crossbeam involving Double free in crossbeam under CWE-415: Double Free.
Which Crossbeam versions are affected?
Affected versions include releases prior to 0.4.1 across affected packages: crossbeam.
What version fixes CVE-2018-20996?
Upgrading to 0.4.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is crossbeam affected?
Yes, crossbeam is affected in releases prior to 0.4.1. Upgrade your dependency to 0.4.1 or later.
What is the CVSS score of CVE-2018-20996?
CVE-2018-20996 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2018-20996?
CVE-2018-20996 is classified under CWE-415: Double Free (The product calls free() twice on the same memory address.).
How can I check crates.io dependencies for CVE-2018-20996?
Run the dependency tree command: 'inspect dependencies for crossbeam'. 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-c3cw-c387-pj65",
  "modified" : "2023-06-13T17:11:24Z",
  "published" : "2021-08-25T20:43:21Z",
  "aliases" : [ "CVE-2018-20996" ],
  "summary" : "Double free in crossbeam",
  "details" : "Even if an element is popped from a queue, crossbeam would run its destructor inside the epoch-based garbage collector. This is a source of double frees.\n\nThe flaw was corrected by wrapping elements inside queues in a ManuallyDrop.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "crossbeam"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.4.0"
      }, {
        "fixed" : "0.4.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-20996"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/crossbeam-rs/crossbeam-epoch/issues/82"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/crossbeam-rs/crossbeam-epoch"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2018-0009.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-415" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T21:24:34Z",
    "nvd_published_at" : "2019-08-26T18:15:11Z"
  }
}