CVE-2021-43558: Moodle/moodle Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-wpfp-q843-v772
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CVSS 6.1
CWE-79
Published
Advisory Summary

CVE-2021-43558 is a MODERATE (CVSS 6.1) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Moodle/moodle libraries in the Packagist ecosystem. The issue involves cross-site scripting in moodle. Remediation is available by upgrading affected packages to version 3.11.4, 3.10.8, 3.9.11.

CVE-2021-43558 at a Glance

CVE Identifier CVE-2021-43558
GHSA Identifier GHSA-wpfp-q843-v772
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Moodle/moodle
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 6.1

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:R/S:C/C:L/I:L/A:N).

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

How to Fix CVE-2021-43558

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: 3.11.4 
Upgrade moodle/moodle to 3.11.4
moodle/moodle fixed: 3.10.8 
Upgrade moodle/moodle to 3.10.8
moodle/moodle fixed: 3.9.11 
Upgrade moodle/moodle to 3.9.11
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-2021-43558, 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 3.11.4), 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-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. 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

A flaw was found in Moodle in versions 3.11 to 3.11.3, 3.10 to 3.10.7, 3.9 to 3.9.10 and earlier unsupported versions. A URL parameter in the filetype site administrator tool required extra sanitizing to prevent a reflected XSS risk.

CVE-2021-43558 Affected Moodle/moodle Versions

3 component(s)
Fixed Versions:
3.11.43.10.83.9.11
Product / Package Ecosystem Affected Versions Fixed Version
moodle/moodle
 Packagist
≥ 3.11.0
< 3.11.4
3.11.4
moodle/moodle
 Packagist
≥ 3.10.0
< 3.10.8
3.10.8
moodle/moodle
 Packagist
≥ 3.9.0
< 3.9.11
3.9.11

References

NVD — CVE-2021-43558 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-43558
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2021515
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=429097

Frequently Asked Questions

What is CVE-2021-43558?
CVE-2021-43558 is a security vulnerability in Moodle/moodle involving Cross-site Scripting in moodle under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Moodle/moodle versions are affected?
Affected versions include releases prior to 3.11.4, 3.10.8, 3.9.11 across affected packages: moodle/moodle.
What version fixes CVE-2021-43558?
Upgrading to 3.11.4, 3.10.8, 3.9.11 (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 3.11.4, 3.10.8, 3.9.11. Upgrade your dependency to 3.11.4, 3.10.8, 3.9.11 or later.
What is the CVSS score of CVE-2021-43558?
CVE-2021-43558 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2021-43558?
CVE-2021-43558 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Packagist dependencies for CVE-2021-43558?
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-wpfp-q843-v772",
  "modified" : "2022-06-17T01:13:12Z",
  "published" : "2021-11-23T00:00:51Z",
  "aliases" : [ "CVE-2021-43558" ],
  "summary" : "Cross-site Scripting in moodle",
  "details" : "A flaw was found in Moodle in versions 3.11 to 3.11.3, 3.10 to 3.10.7, 3.9 to 3.9.10 and earlier unsupported versions. A URL parameter in the filetype site administrator tool required extra sanitizing to prevent a reflected XSS risk.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.11.0"
      }, {
        "fixed" : "3.11.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.10.0"
      }, {
        "fixed" : "3.10.8"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "moodle/moodle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.9.0"
      }, {
        "fixed" : "3.9.11"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-43558"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2021515"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/moodle/moodle"
  }, {
    "type" : "WEB",
    "url" : "https://moodle.org/mod/forum/discuss.php?d=429097"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-17T01:13:12Z",
    "nvd_published_at" : "2021-11-22T16:15:00Z"
  }
}