CVE-2017-6920: Drupal/core Drupal PECL YAML Parser Unsafe Vulnerability

CRITICAL
Advisory Identifier: GHSA-9c24-g32g-35rj
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CVSS 9.8
CWE-94
Published
Advisory Summary

CVE-2017-6920 is a CRITICAL (CVSS 9.8) drupal pecl yaml parser unsafe vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Drupal/core libraries in the Packagist ecosystem. The issue involves drupal pecl yaml parser unsafe object handling. Remediation is available by upgrading affected packages to version 8.3.4.

CVE-2017-6920 at a Glance

CVE Identifier CVE-2017-6920
GHSA Identifier GHSA-9c24-g32g-35rj
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-94: Improper Control of Generation of Code ('Code Injection')
Affected Product Drupal/core
Package Ecosystem Packagist
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:3.0/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-2017-6920

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

drupal/core fixed: 8.3.4 
Upgrade drupal/core to 8.3.4
drupal/drupal fixed: 8.3.4 
Upgrade drupal/drupal to 8.3.4
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 drupal/core

How to Check if You Are Affected

To determine whether your application is affected by CVE-2017-6920, inspect your project dependencies for Drupal/core:

inspect dependencies for drupal/core

Analyze the terminal output to locate any version of Drupal/core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 8.3.4), 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-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 Drupal/core, 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

Drupal core 8 before versions 8.3.4 allows remote attackers to execute arbitrary code due to the PECL YAML parser not handling PHP objects safely during certain operations.

CVE-2017-6920 Affected Drupal/core Versions

2 component(s)
Fixed Versions:
8.3.4
Product / Package Ecosystem Affected Versions Fixed Version
drupal/core
 Packagist
≥ 8.0
< 8.3.4
8.3.4
drupal/drupal
 Packagist
≥ 8.0
< 8.3.4
8.3.4

References

NVD — CVE-2017-6920 NVD
https://nvd.nist.gov/vuln/detail/CVE-2017-6920
Drupal/core Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/core/CVE-2017-6920.yaml
Drupal/core Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/drupal/CVE-2017-6920.yaml
Drupal/core Source Repository REPOSITORY
https://github.com/drupal/core
www.drupal.org/sa-core-2017-003 WEB
https://www.drupal.org/SA-CORE-2017-003
Drupal/core Security Information SECURITY
https://www.drupal.org/forum/newsletters/security-advisories-for-drupal-core/2017-06-21/drupal-core-multiple
Drupal/core Security Information SECURITY
http://www.securityfocus.com/bid/99211
Drupal/core Security Information SECURITY
http://www.securitytracker.com/id/1038781

Frequently Asked Questions

What is CVE-2017-6920?
CVE-2017-6920 is a security vulnerability in Drupal/core involving Drupal PECL YAML parser unsafe object handling under CWE-94: Improper Control of Generation of Code ('Code Injection').
Which Drupal/core versions are affected?
Affected versions include releases prior to 8.3.4 across affected packages: drupal/core, drupal/drupal.
What version fixes CVE-2017-6920?
Upgrading to 8.3.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is drupal/core affected?
Yes, drupal/core is affected in releases prior to 8.3.4. Upgrade your dependency to 8.3.4 or later.
Is drupal/drupal affected?
Yes, drupal/drupal is affected in releases prior to 8.3.4. Upgrade your dependency to 8.3.4 or later.
What is the CVSS score of CVE-2017-6920?
CVE-2017-6920 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2017-6920?
CVE-2017-6920 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 Packagist dependencies for CVE-2017-6920?
Run the dependency tree command: 'inspect dependencies for drupal/core'. 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-9c24-g32g-35rj",
  "modified" : "2024-04-23T17:21:10Z",
  "published" : "2022-05-14T02:57:07Z",
  "aliases" : [ "CVE-2017-6920" ],
  "summary" : "Drupal PECL YAML parser unsafe object handling",
  "details" : "Drupal core 8 before versions 8.3.4 allows remote attackers to execute arbitrary code due to the PECL YAML parser not handling PHP objects safely during certain operations.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "drupal/core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0"
      }, {
        "fixed" : "8.3.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "drupal/drupal"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0"
      }, {
        "fixed" : "8.3.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2017-6920"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/core/CVE-2017-6920.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/drupal/CVE-2017-6920.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/drupal/core"
  }, {
    "type" : "WEB",
    "url" : "https://www.drupal.org/SA-CORE-2017-003"
  }, {
    "type" : "WEB",
    "url" : "https://www.drupal.org/forum/newsletters/security-advisories-for-drupal-core/2017-06-21/drupal-core-multiple"
  }, {
    "type" : "WEB",
    "url" : "http://www.securityfocus.com/bid/99211"
  }, {
    "type" : "WEB",
    "url" : "http://www.securitytracker.com/id/1038781"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-04-23T17:21:09Z",
    "nvd_published_at" : "2018-08-06T15:29:00Z"
  }
}