CVE-2021-38191: Tokio Race Condition Vulnerability

MODERATE
Advisory Identifier: GHSA-2grh-hm3w-w7hv
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CVSS 5.9
CWE-366 CWE-362
Published
Advisory Summary

CVE-2021-38191 is a MODERATE (CVSS 5.9) race condition vulnerability (CWE-366: Race Condition within a Thread) affecting Tokio libraries in the crates.io ecosystem. The issue involves race condition in tokio. Remediation is available by upgrading affected packages to version 1.8.1, 1.7.2, 1.6.3, 1.5.1.

CVE-2021-38191 at a Glance

CVE Identifier CVE-2021-38191
GHSA Identifier GHSA-2grh-hm3w-w7hv
Severity MODERATE
CVSS v3.1 Base Score 5.9
CWE Classification CWE-366: Race Condition within a Thread
Affected Product Tokio
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 5.9

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

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
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-2021-38191

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

tokio fixed: 1.8.1 
Upgrade tokio to 1.8.1
tokio fixed: 1.7.2 
Upgrade tokio to 1.7.2
tokio fixed: 1.6.3 
Upgrade tokio to 1.6.3
tokio fixed: 1.5.1 
Upgrade tokio to 1.5.1
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 tokio

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-38191, inspect your project dependencies for Tokio:

inspect dependencies for tokio

Analyze the terminal output to locate any version of Tokio in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.8.1), 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-366: Race Condition within a Thread, where if two threads of execution use a resource simultaneously, there exists the possibility that resources may be used while invalid, in turn making the state of execution undefined. In Tokio, 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

When aborting a task with JoinHandle::abort, the future is dropped in the thread calling abort if the task is not currently being executed. This is incorrect for tasks spawned on a LocalSet. This can easily result in race conditions as many projects use Rc or RefCell in their Tokio tasks for better performance.

CVE-2021-38191 Affected Tokio Versions

4 component(s)
Fixed Versions:
1.8.11.7.21.6.31.5.1
Product / Package Ecosystem Affected Versions Fixed Version
tokio
 crates.io
≥ 1.8.0
< 1.8.1
1.8.1
tokio
 crates.io
≥ 1.7.0
< 1.7.2
1.7.2
tokio
 crates.io
≥ 1.6.0
< 1.6.3
1.6.3
tokio
 crates.io
≥ 0.3.0
< 1.5.1
1.5.1

References

NVD — CVE-2021-38191 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-38191
Tokio Source Repository REPOSITORY
https://github.com/tokio-rs/tokio/issues/3929
Tokio Source Repository REPOSITORY
https://github.com/tokio-rs/tokio
raw.githubusercontent.com/rustsec/advisory-db... WEB
https://raw.githubusercontent.com/rustsec/advisory-db/main/crates/tokio/RUSTSEC-2021-0072.md
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2021-0072.html

Frequently Asked Questions

What is CVE-2021-38191?
CVE-2021-38191 is a security vulnerability in Tokio involving Race condition in tokio under CWE-366: Race Condition within a Thread.
Which Tokio versions are affected?
Affected versions include releases prior to 1.8.1, 1.7.2, 1.6.3, 1.5.1 across affected packages: tokio.
What version fixes CVE-2021-38191?
Upgrading to 1.8.1, 1.7.2, 1.6.3, 1.5.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tokio affected?
Yes, tokio is affected in releases prior to 1.8.1, 1.7.2, 1.6.3, 1.5.1. Upgrade your dependency to 1.8.1, 1.7.2, 1.6.3, 1.5.1 or later.
What is the CVSS score of CVE-2021-38191?
CVE-2021-38191 has a CVSS v3.1 base score of 5.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-38191?
CVE-2021-38191 is classified under CWE-366: Race Condition within a Thread (If two threads of execution use a resource simultaneously, there exists the possibility that resources may be used while invalid, in turn making the state of execution undefined.).
How can I check crates.io dependencies for CVE-2021-38191?
Run the dependency tree command: 'inspect dependencies for tokio'. 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-2grh-hm3w-w7hv",
  "modified" : "2023-06-13T22:08:56Z",
  "published" : "2021-08-25T20:55:51Z",
  "aliases" : [ "CVE-2021-38191" ],
  "summary" : "Race condition in tokio",
  "details" : "When aborting a task with JoinHandle::abort, the future is dropped in the thread calling abort if the task is not currently being executed. This is incorrect for tasks spawned on a LocalSet. This can easily result in race conditions as many projects use Rc or RefCell in their Tokio tasks for better performance.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tokio"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.8.0"
      }, {
        "fixed" : "1.8.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tokio"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.7.0"
      }, {
        "fixed" : "1.7.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tokio"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.6.0"
      }, {
        "fixed" : "1.6.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tokio"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.3.0"
      }, {
        "fixed" : "1.5.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-38191"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tokio-rs/tokio/issues/3929"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tokio-rs/tokio"
  }, {
    "type" : "WEB",
    "url" : "https://raw.githubusercontent.com/rustsec/advisory-db/main/crates/tokio/RUSTSEC-2021-0072.md"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2021-0072.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-362", "CWE-366" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-18T21:30:23Z",
    "nvd_published_at" : "2021-08-08T06:15:00Z"
  }
}