CVE-2020-35875: Tokio rustls Excessive Memory Usage Vulnerability

HIGH
Advisory Identifier: GHSA-2jfv-g3fh-xq3v
Share
CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2020-35875 is a HIGH (CVSS 7.5) excessive memory usage vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Tokio rustls libraries in the crates.io ecosystem. The issue involves excessive memory usage in tokio-rustls. Remediation is available by upgrading affected packages to version 0.12.3, 0.13.1.

CVE-2020-35875 at a Glance

CVE Identifier CVE-2020-35875
GHSA Identifier GHSA-2jfv-g3fh-xq3v
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Tokio rustls
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-2020-35875

To remediate this vulnerability, upgrade all affected Tokio rustls 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-rustls fixed: 0.12.3 
Upgrade tokio-rustls to 0.12.3
tokio-rustls fixed: 0.13.1 
Upgrade tokio-rustls to 0.13.1
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-rustls

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-35875, inspect your project dependencies for Tokio rustls:

inspect dependencies for tokio-rustls

Analyze the terminal output to locate any version of Tokio rustls in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.12.3), 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-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Tokio rustls, 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

tokio-rustls does not call process_new_packets immediately after read, so the expected termination condition wants_read always returns true. As long as new incoming data arrives faster than it is processed and the reader does not return pending, data will be buffered. This may cause DoS.

CVE-2020-35875 Affected Tokio rustls Versions

2 component(s)
Fixed Versions:
0.12.30.13.1
Product / Package Ecosystem Affected Versions Fixed Version
tokio-rustls
 crates.io
≥ 0.12.0
< 0.12.3
0.12.3
tokio-rustls
 crates.io
≥ 0.13.0
< 0.13.1
0.13.1

References

NVD — CVE-2020-35875 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-35875
Tokio rustls Source Repository REPOSITORY
https://github.com/tokio-rs/tls/pull/14
Tokio rustls Source Repository REPOSITORY
https://github.com/tokio-rs/tls
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2020-0019.html

Frequently Asked Questions

What is CVE-2020-35875?
CVE-2020-35875 is a security vulnerability in Tokio rustls involving Excessive memory usage in tokio-rustls under CWE-400: Uncontrolled Resource Consumption.
Which Tokio rustls versions are affected?
Affected versions include releases prior to 0.12.3, 0.13.1 across affected packages: tokio-rustls.
What version fixes CVE-2020-35875?
Upgrading to 0.12.3, 0.13.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tokio-rustls affected?
Yes, tokio-rustls is affected in releases prior to 0.12.3, 0.13.1. Upgrade your dependency to 0.12.3, 0.13.1 or later.
What is the CVSS score of CVE-2020-35875?
CVE-2020-35875 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-2020-35875?
CVE-2020-35875 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check crates.io dependencies for CVE-2020-35875?
Run the dependency tree command: 'inspect dependencies for tokio-rustls'. 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-2jfv-g3fh-xq3v",
  "modified" : "2023-06-13T21:56:58Z",
  "published" : "2021-08-25T20:46:54Z",
  "aliases" : [ "CVE-2020-35875" ],
  "summary" : "Excessive memory usage in tokio-rustls",
  "details" : "tokio-rustls does not call process_new_packets immediately after read, so the expected termination condition wants_read always returns true. As long as new incoming data arrives faster than it is processed and the reader does not return pending, data will be buffered. This may cause DoS.",
  "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" : "tokio-rustls"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.12.0"
      }, {
        "fixed" : "0.12.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tokio-rustls"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.13.0"
      }, {
        "fixed" : "0.13.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-35875"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tokio-rs/tls/pull/14"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tokio-rs/tls"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2020-0019.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T21:19:01Z",
    "nvd_published_at" : null
  }
}