CVE-2020-6174: Tuf Incorrect Threshold Signature Computation Vulnerability

CRITICAL
Advisory Identifier: GHSA-pwqf-9h7j-7mv8
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CVSS 9.8
CWE-347
Published
Advisory Summary

CVE-2020-6174 is a CRITICAL (CVSS 9.8) incorrect threshold signature computation vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting Tuf libraries in the PyPI ecosystem. The issue involves incorrect threshold signature computation in tuf. Remediation is available by upgrading affected packages to version 0.12.2.

CVE-2020-6174 at a Glance

CVE Identifier CVE-2020-6174
GHSA Identifier GHSA-pwqf-9h7j-7mv8
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product Tuf
Package Ecosystem PyPI
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:3.1/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-2020-6174

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

tuf fixed: 0.12.2 
pip install tuf>=0.12.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show tuf

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2020-6174, inspect your installed packages using pip:

pip show tuf

Analyze the terminal output to locate any version of Tuf in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.12.2), your application is affected.

Note: The pip show tuf command checks currently installed packages in your active Python environment.

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 Tuf, 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 Metadadata signature verification, as used in `tuf.client.updater`, counted each of multiple signatures with identical authorized keyids separately towards the threshold. Therefore, an attacker with access to a valid signing key could create multiple valid signatures in order to meet the minimum threshold of keys before the metadata was considered valid. The tuf maintainers would like to thank Erik MacLean of Analog Devices, Inc. for reporting this issue. ### Patches A [fix](https://github.com/theupdateframework/tuf/pull/974) is available in version [0.12.2](https://github.com/theupdateframework/tuf/releases/tag/v0.12.2) or newer. ### Workarounds No workarounds are known for this issue. ### References * [CVE-2020-6174](https://nvd.nist.gov/vuln/detail/CVE-2020-6174) * Pull request resolving the issue [PR 974](https://github.com/theupdateframework/tuf/pull/974)

CVE-2020-6174 Affected Tuf Versions

1 component(s)
Fixed Versions:
0.12.2
Product / Package Ecosystem Affected Versions Fixed Version
tuf
pypi/tuf
PyPI
< 0.12.2
0.12.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/theupdateframework/tuf/security/advisories/GHSA-pwqf-9h7j-7mv8
NVD — CVE-2020-6174 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-6174
Tuf Source Repository REPOSITORY
https://github.com/theupdateframework/tuf/pull/974
Security Fix Commit FIX COMMIT
https://github.com/theupdateframework/python-tuf/commit/2977188139d065ff3356c3cb4aec60c582b57e0e
Tuf Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/tuf/PYSEC-2020-147.yaml
Tuf Source Repository REPOSITORY
https://github.com/theupdateframework/tuf
Tuf Release RELEASE
https://github.com/theupdateframework/tuf/releases/tag/v0.12.2

Frequently Asked Questions

What is CVE-2020-6174?
CVE-2020-6174 is a security vulnerability in Tuf involving Incorrect threshold signature computation in TUF under CWE-347: Improper Verification of Cryptographic Signature.
Which Tuf versions are affected?
Affected versions include releases prior to 0.12.2 across affected packages: tuf.
What version fixes CVE-2020-6174?
Upgrading to 0.12.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tuf affected?
Yes, tuf is affected in releases prior to 0.12.2. Upgrade your dependency to 0.12.2 or later.
What is the CVSS score of CVE-2020-6174?
CVE-2020-6174 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2020-6174?
CVE-2020-6174 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 PyPI dependencies for CVE-2020-6174?
Run the dependency tree command: 'pip show tuf'. 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-pwqf-9h7j-7mv8",
  "modified" : "2024-11-18T22:40:36Z",
  "published" : "2020-08-21T16:25:26Z",
  "aliases" : [ "CVE-2020-6174" ],
  "summary" : "Incorrect threshold signature computation in TUF",
  "details" : "### Impact\nMetadadata signature verification, as used in `tuf.client.updater`, counted each of multiple signatures with identical authorized keyids  separately towards the threshold. Therefore, an attacker with access to a valid signing key could create multiple valid signatures in order to meet the minimum threshold of keys before the metadata was considered valid.\n\nThe tuf maintainers would like to thank Erik MacLean of Analog Devices, Inc. for reporting this issue.\n\n### Patches\nA [fix](https://github.com/theupdateframework/tuf/pull/974) is available in version [0.12.2](https://github.com/theupdateframework/tuf/releases/tag/v0.12.2) or newer.\n\n### Workarounds\nNo workarounds are known for this issue.\n\n### References\n* [CVE-2020-6174](https://nvd.nist.gov/vuln/detail/CVE-2020-6174)\n* Pull request resolving the issue [PR 974](https://github.com/theupdateframework/tuf/pull/974)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "tuf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.12.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/tuf/security/advisories/GHSA-pwqf-9h7j-7mv8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-6174"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/tuf/pull/974"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/commit/2977188139d065ff3356c3cb4aec60c582b57e0e"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/tuf/PYSEC-2020-147.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/theupdateframework/tuf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/tuf/releases/tag/v0.12.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-08-21T16:25:02Z",
    "nvd_published_at" : null
  }
}