CVE-2021-20187: Moodle/moodle Moodle Arbitrary PHP Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-2jrm-gww7-wch2
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CVSS 7.2
CWE-829 CWE-94
Published
Advisory Summary

CVE-2021-20187 is a HIGH (CVSS 7.2) moodle arbitrary php code execution vulnerability (CWE-829: Inclusion of Functionality from Untrusted Control Sphere) affecting Moodle/moodle libraries in the Packagist ecosystem. The issue involves moodle arbitrary php code execution by site admins via shibboleth configuration. Remediation is available by upgrading affected packages to version 3.5.16, 3.8.7, 3.9.4, 3.10.1.

CVE-2021-20187 at a Glance

CVE Identifier CVE-2021-20187
GHSA Identifier GHSA-2jrm-gww7-wch2
Severity HIGH
CVSS v3.1 Base Score 7.2
CWE Classification CWE-829: Inclusion of Functionality from Untrusted Control Sphere
Affected Product Moodle/moodle
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 7.2

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required High (PR:H)
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-2021-20187

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

moodle/moodle fixed: 3.5.16 
Upgrade moodle/moodle to 3.5.16
moodle/moodle fixed: 3.8.7 
Upgrade moodle/moodle to 3.8.7
moodle/moodle fixed: 3.9.4 
Upgrade moodle/moodle to 3.9.4
moodle/moodle fixed: 3.10.1 
Upgrade moodle/moodle to 3.10.1
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 moodle/moodle

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-20187, inspect your project dependencies for Moodle/moodle:

inspect dependencies for moodle/moodle

Analyze the terminal output to locate any version of Moodle/moodle in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.5.16), 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-829: Inclusion of Functionality from Untrusted Control Sphere, where the product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere. In Moodle/moodle, 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

It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that it was possible for site administrators to execute arbitrary PHP scripts via a PHP include used during Shibboleth authentication.

CVE-2021-20187 Affected Moodle/moodle Versions

4 component(s)
Fixed Versions:
3.5.163.8.73.9.43.10.1
Product / Package Ecosystem Affected Versions Fixed Version
moodle/moodle
 Packagist
≥ 3.5
< 3.5.16
3.5.16
moodle/moodle
 Packagist
≥ 3.8
< 3.8.7
3.8.7
moodle/moodle
 Packagist
< 3.9.4
≥ 3.9
3.9.4
moodle/moodle
 Packagist
≥ 3.10
< 3.10.1
3.10.1

References

NVD — CVE-2021-20187 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-20187
Moodle/moodle Source Repository REPOSITORY
https://github.com/moodle/moodle
moodle.org/mod/forum/discuss.p... WEB
https://moodle.org/mod/forum/discuss.php?d=417171

Frequently Asked Questions

What is CVE-2021-20187?
CVE-2021-20187 is a security vulnerability in Moodle/moodle involving Moodle Arbitrary PHP code execution by site admins via Shibboleth configuration under CWE-829: Inclusion of Functionality from Untrusted Control Sphere.
Which Moodle/moodle versions are affected?
Affected versions include releases prior to 3.5.16, 3.8.7, 3.9.4, 3.10.1 across affected packages: moodle/moodle.
What version fixes CVE-2021-20187?
Upgrading to 3.5.16, 3.8.7, 3.9.4, 3.10.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is moodle/moodle affected?
Yes, moodle/moodle is affected in releases prior to 3.5.16, 3.8.7, 3.9.4, 3.10.1. Upgrade your dependency to 3.5.16, 3.8.7, 3.9.4, 3.10.1 or later.
What is the CVSS score of CVE-2021-20187?
CVE-2021-20187 has a CVSS v3.1 base score of 7.2 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-20187?
CVE-2021-20187 is classified under CWE-829: Inclusion of Functionality from Untrusted Control Sphere (The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere.).
How can I check Packagist dependencies for CVE-2021-20187?
Run the dependency tree command: 'inspect dependencies for moodle/moodle'. 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-2jrm-gww7-wch2",
  "modified" : "2024-04-23T23:37:33Z",
  "published" : "2022-05-24T17:40:31Z",
  "aliases" : [ "CVE-2021-20187" ],
  "summary" : "Moodle Arbitrary PHP code execution by site admins via Shibboleth configuration",
  "details" : "It was found in Moodle before version 3.10.1, 3.9.4, 3.8.7 and 3.5.16 that it was possible for site administrators to execute arbitrary PHP scripts via a PHP include used during Shibboleth authentication.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.5"
      }, {
        "fixed" : "3.5.16"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.8"
      }, {
        "fixed" : "3.8.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.9"
      }, {
        "fixed" : "3.9.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.10"
      }, {
        "fixed" : "3.10.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-20187"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/moodle/moodle"
  }, {
    "type" : "WEB",
    "url" : "https://moodle.org/mod/forum/discuss.php?d=417171"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-829", "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-04-23T23:37:33Z",
    "nvd_published_at" : "2021-01-28T19:15:00Z"
  }
}