CVE-2020-15093: Tough Improper Verification Of Signature Threshold Vulnerability

HIGH
Advisory Identifier: GHSA-5q2r-92f9-4m49
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CVSS 8.6
CWE-347
Published
Advisory Summary

CVE-2020-15093 is a HIGH (CVSS 8.6) improper verification of signature threshold vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting Tough libraries in the crates.io ecosystem. The issue involves improper verification of signature threshold in tough. Remediation is available by upgrading affected packages to version 0.7.1.

CVE-2020-15093 at a Glance

CVE Identifier CVE-2020-15093
GHSA Identifier GHSA-5q2r-92f9-4m49
Severity HIGH
CVSS v3.1 Base Score 8.6
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product Tough
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 8.6

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:C/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2020-15093

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

tough fixed: 0.7.1 
Upgrade tough to 0.7.1
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 tough

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-15093, inspect your project dependencies for Tough:

inspect dependencies for tough

Analyze the terminal output to locate any version of Tough in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.7.1), 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-347: Improper Verification of Cryptographic Signature, where the product does not verify, or incorrectly verifies, the cryptographic signature for data. In Tough, 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

## Impact The tough library, prior to 0.7.1, does not properly verify the uniqueness of keys in the signatures provided to meet the threshold of cryptographic signatures. It allows someone with access to a valid signing key to create multiple valid signatures in order to circumvent TUF requiring a minimum threshold of unique keys before the metadata is considered valid. AWS would like to thank Erick Tryzelaar of the Google Fuchsia Team for reporting this issue. ## Patches A fix is available in version 0.7.1. ## Workarounds No workarounds to this issue are known. ## References CVE-2020-6174 is assigned to the same issue in the TUF reference implementation. https://github.com/theupdateframework/tuf/pull/974 https://nvd.nist.gov/vuln/detail/CVE-2020-6174 ## For more information If you have any questions or comments about this advisory, [contact AWS Security](https://aws.amazon.com/security/vulnerability-reporting/) at [aws-security@amazon.com](mailto:aws-security@amazon.com).

CVE-2020-15093 Affected Tough Versions

1 component(s)
Fixed Versions:
0.7.1
Product / Package Ecosystem Affected Versions Fixed Version
tough
 crates.io
< 0.7.1
0.7.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/awslabs/tough/security/advisories/GHSA-5q2r-92f9-4m49
NVD — CVE-2020-15093 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-15093
Tough Source Repository REPOSITORY
https://github.com/theupdateframework/tuf/pull/974
Security Fix Commit FIX COMMIT
https://github.com/theupdateframework/tuf/commit/2977188139d065ff3356c3cb4aec60c582b57e0e
Tough Source Repository REPOSITORY
https://github.com/awslabs/tough
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2020-0024.html

Frequently Asked Questions

What is CVE-2020-15093?
CVE-2020-15093 is a security vulnerability in Tough involving Improper verification of signature threshold in tough under CWE-347: Improper Verification of Cryptographic Signature.
Which Tough versions are affected?
Affected versions include releases prior to 0.7.1 across affected packages: tough.
What version fixes CVE-2020-15093?
Upgrading to 0.7.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tough affected?
Yes, tough is affected in releases prior to 0.7.1. Upgrade your dependency to 0.7.1 or later.
What is the CVSS score of CVE-2020-15093?
CVE-2020-15093 has a CVSS v3.1 base score of 8.6 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N.
What CWE is associated with CVE-2020-15093?
CVE-2020-15093 is classified under CWE-347: Improper Verification of Cryptographic Signature (The product does not verify, or incorrectly verifies, the cryptographic signature for data.).
How can I check crates.io dependencies for CVE-2020-15093?
Run the dependency tree command: 'inspect dependencies for tough'. 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-5q2r-92f9-4m49",
  "modified" : "2021-10-27T17:03:38Z",
  "published" : "2021-08-25T20:56:55Z",
  "aliases" : [ "CVE-2020-15093" ],
  "summary" : "Improper verification of signature threshold in tough",
  "details" : "## Impact\n\nThe tough library, prior to 0.7.1, does not properly verify the uniqueness of keys in the signatures provided to meet the threshold of cryptographic signatures. It allows someone with access to a valid signing key to create multiple valid signatures in order to circumvent TUF requiring a minimum threshold of unique keys before the metadata is considered valid.\n\nAWS would like to thank Erick Tryzelaar of the Google Fuchsia Team for reporting this issue. \n\n## Patches\n\nA fix is available in version 0.7.1.\n\n## Workarounds\n\nNo workarounds to this issue are known.\n\n## References\n\nCVE-2020-6174 is assigned to the same issue in the TUF reference implementation.\n\nhttps://github.com/theupdateframework/tuf/pull/974\nhttps://nvd.nist.gov/vuln/detail/CVE-2020-6174\n\n## For more information\n\nIf you have any questions or comments about this advisory, [contact AWS Security](https://aws.amazon.com/security/vulnerability-reporting/) at [aws-security@amazon.com](mailto:aws-security@amazon.com).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tough"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.7.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/awslabs/tough/security/advisories/GHSA-5q2r-92f9-4m49"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-15093"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/tuf/pull/974"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/tuf/commit/2977188139d065ff3356c3cb4aec60c582b57e0e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/awslabs/tough"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2020-0024.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-18T20:40:25Z",
    "nvd_published_at" : "2020-07-09T19:15:00Z"
  }
}