CVE-2018-20133: Ymlref Code Injection Vulnerability

CRITICAL
Advisory Identifier: GHSA-8r8j-xvfj-36f9
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CVSS 9.8
CWE-94
Published
Advisory Summary

CVE-2018-20133 is a CRITICAL (CVSS 9.8) code injection vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Ymlref libraries in the PyPI ecosystem. The issue involves code injection in ymlref. Remediation is available in the latest vendor maintenance releases.

CVE-2018-20133 at a Glance

CVE Identifier CVE-2018-20133
GHSA Identifier GHSA-8r8j-xvfj-36f9
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-94: Improper Control of Generation of Code ('Code Injection')
Affected Product Ymlref
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-2018-20133

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

ymlref fixed: Latest secure release 
pip install ymlref>=Latest secure release
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 ymlref

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2018-20133, inspect your installed packages using pip:

pip show ymlref

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

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-94: Improper Control of Generation of Code ('Code Injection'), where the product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. In Ymlref, 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

ymlref is a library that allows to load Yaml documents and resolve JSON-pointer references inside them. ymlref versions up to 0.1.1 allow code injection.

CVE-2018-20133 Affected Ymlref Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
ymlref
pypi/ymlref
PyPI
≤ 0.1.1

References

NVD — CVE-2018-20133 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-20133
Ymlref Source Repository REPOSITORY
https://github.com/dexter2206/ymlref/issues/2
Ymlref Source Repository REPOSITORY
https://github.com/dexter2206/ymlref
Ymlref Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/ymlref/PYSEC-2018-103.yaml

Frequently Asked Questions

What is CVE-2018-20133?
CVE-2018-20133 is a security vulnerability in Ymlref involving Code injection in ymlref under CWE-94: Improper Control of Generation of Code ('Code Injection').
Which Ymlref versions are affected?
Affected versions include releases prior to current release patches across affected packages: ymlref.
What version fixes CVE-2018-20133?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is ymlref affected?
Yes, ymlref is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2018-20133?
CVE-2018-20133 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-2018-20133?
CVE-2018-20133 is classified under CWE-94: Improper Control of Generation of Code ('Code Injection') (The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.).
How can I check PyPI dependencies for CVE-2018-20133?
Run the dependency tree command: 'pip show ymlref'. 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-8r8j-xvfj-36f9",
  "modified" : "2024-11-19T18:07:18Z",
  "published" : "2018-12-19T19:25:14Z",
  "aliases" : [ "CVE-2018-20133" ],
  "summary" : "Code injection in ymlref",
  "details" : "ymlref is a library that allows to load Yaml documents and resolve JSON-pointer references inside them. ymlref versions up to 0.1.1 allow code injection.",
  "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" : "ymlref"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-20133"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/dexter2206/ymlref/issues/2"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/dexter2206/ymlref"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/ymlref/PYSEC-2018-103.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-06-16T21:26:33Z",
    "nvd_published_at" : null
  }
}