CVE-2020-35905: MutexGuard :map Can Cause A Data Vulnerability

MODERATE
Advisory Identifier: GHSA-rh4w-94hh-9943
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CVSS 4.7
CWE-362
Published
Advisory Summary

CVE-2020-35905 is a MODERATE (CVSS 4.7) :map can cause a data vulnerability (CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')) affecting MutexGuard libraries in the crates.io ecosystem. The issue involves :map can cause a data race in safe code. Remediation is available by upgrading affected packages to version 0.3.7.

CVE-2020-35905 at a Glance

CVE Identifier CVE-2020-35905
GHSA Identifier GHSA-rh4w-94hh-9943
Severity MODERATE
CVSS v3.1 Base Score 4.7
CWE Classification CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Affected Product MutexGuard
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 4.7

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

Attack Vector Local (AV:L)
Attack Complexity High (AC:H)
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-2020-35905

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

futures-util fixed: 0.3.7 
Upgrade futures-util to 0.3.7
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 futures-util

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-35905, inspect your project dependencies for MutexGuard:

inspect dependencies for futures-util

Analyze the terminal output to locate any version of MutexGuard in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.3.7), 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-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'), where the product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently. In MutexGuard, 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

Affected versions of the crate had a Send/Sync implementation for MappedMutexGuard that only considered variance on T, while MappedMutexGuard dereferenced to U. This could of led to data races in safe Rust code when a closure used in MutexGuard::map() returns U that is unrelated to T. The issue was fixed by fixing Send and Sync implementations, and by adding a PhantomData<&'a mut U> marker to the MappedMutexGuard type to tell the compiler that the guard is over U too.

CVE-2020-35905 Affected MutexGuard Versions

1 component(s)
Fixed Versions:
0.3.7
Product / Package Ecosystem Affected Versions Fixed Version
futures-util
 crates.io
≥ 0.3.2
< 0.3.7
0.3.7

References

NVD — CVE-2020-35905 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-35905
MutexGuard Source Repository REPOSITORY
https://github.com/rust-lang/futures-rs/issues/2239
MutexGuard Source Repository REPOSITORY
https://github.com/rust-lang/futures-rs
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2020-0059.html

Frequently Asked Questions

What is CVE-2020-35905?
CVE-2020-35905 is a security vulnerability in MutexGuard involving :map can cause a data race in safe code under CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition').
Which MutexGuard versions are affected?
Affected versions include releases prior to 0.3.7 across affected packages: futures-util.
What version fixes CVE-2020-35905?
Upgrading to 0.3.7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is futures-util affected?
Yes, futures-util is affected in releases prior to 0.3.7. Upgrade your dependency to 0.3.7 or later.
What is the CVSS score of CVE-2020-35905?
CVE-2020-35905 has a CVSS v3.1 base score of 4.7 (MODERATE) with vector string CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2020-35905?
CVE-2020-35905 is classified under CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') (The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.).
How can I check crates.io dependencies for CVE-2020-35905?
Run the dependency tree command: 'inspect dependencies for futures-util'. 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-rh4w-94hh-9943",
  "modified" : "2023-06-13T17:24:13Z",
  "published" : "2022-05-24T17:37:49Z",
  "aliases" : [ "CVE-2020-35905" ],
  "summary" : "MutexGuard::map can cause a data race in safe code",
  "details" : "Affected versions of the crate had a Send/Sync implementation for MappedMutexGuard that only considered variance on T, while MappedMutexGuard dereferenced to U.\n\nThis could of led to data races in safe Rust code when a closure used in MutexGuard::map() returns U that is unrelated to T.\n\nThe issue was fixed by fixing Send and Sync implementations, and by adding a PhantomData<&'a mut U> marker to the MappedMutexGuard type to tell the compiler that the guard is over U too.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "futures-util"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.3.2"
      }, {
        "fixed" : "0.3.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-35905"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rust-lang/futures-rs/issues/2239"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rust-lang/futures-rs"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2020-0059.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-362" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-16T23:55:12Z",
    "nvd_published_at" : "2020-12-31T09:15:00Z"
  }
}