CVE-2021-4072: Elgg/elgg Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-2xw8-j43j-5vxp
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CVSS 5.4
CWE-79
Published
Advisory Summary

CVE-2021-4072 is a MODERATE (CVSS 5.4) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Elgg/elgg libraries in the Packagist ecosystem. The issue involves elgg is vulnerable to cross-site scripting. Remediation is available by upgrading affected packages to version 3.3.24.

CVE-2021-4072 at a Glance

CVE Identifier CVE-2021-4072
GHSA Identifier GHSA-2xw8-j43j-5vxp
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Elgg/elgg
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 5.4

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

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
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-2021-4072

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

elgg/elgg fixed: 3.3.24 
Upgrade elgg/elgg to 3.3.24
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 elgg/elgg

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-4072, inspect your project dependencies for Elgg/elgg:

inspect dependencies for elgg/elgg

Analyze the terminal output to locate any version of Elgg/elgg in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.3.24), 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 Elgg/elgg, 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

elgg is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVE-2021-4072 Affected Elgg/elgg Versions

1 component(s)
Fixed Versions:
3.3.24
Product / Package Ecosystem Affected Versions Fixed Version
elgg/elgg
 Packagist
< 3.3.24
3.3.24

References

NVD — CVE-2021-4072 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-4072
Security Fix Commit FIX COMMIT
https://github.com/elgg/elgg/commit/c30b17bf75256ed3fcc84e2083147cc3951423d0
Elgg/elgg Source Repository REPOSITORY
https://github.com/elgg/elgg
huntr.dev/bounties/74034253-7... WEB
https://huntr.dev/bounties/74034253-732a-4251-a0f9-eca5f576c955

Frequently Asked Questions

What is CVE-2021-4072?
CVE-2021-4072 is a security vulnerability in Elgg/elgg involving elgg is vulnerable to Cross-site Scripting under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Elgg/elgg versions are affected?
Affected versions include releases prior to 3.3.24 across affected packages: elgg/elgg.
What version fixes CVE-2021-4072?
Upgrading to 3.3.24 (or the latest patched release for your respective branch) resolves the vulnerability.
Is elgg/elgg affected?
Yes, elgg/elgg is affected in releases prior to 3.3.24. Upgrade your dependency to 3.3.24 or later.
What is the CVSS score of CVE-2021-4072?
CVE-2021-4072 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2021-4072?
CVE-2021-4072 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-2021-4072?
Run the dependency tree command: 'inspect dependencies for elgg/elgg'. 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-2xw8-j43j-5vxp",
  "modified" : "2022-01-05T17:56:06Z",
  "published" : "2022-01-06T21:35:42Z",
  "aliases" : [ "CVE-2021-4072" ],
  "summary" : "elgg is vulnerable to Cross-site Scripting",
  "details" : "elgg is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "elgg/elgg"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.3.24"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-4072"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/elgg/elgg/commit/c30b17bf75256ed3fcc84e2083147cc3951423d0"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/elgg/elgg"
  }, {
    "type" : "WEB",
    "url" : "https://huntr.dev/bounties/74034253-732a-4251-a0f9-eca5f576c955"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-01-05T17:56:06Z",
    "nvd_published_at" : "2021-12-24T14:15:00Z"
  }
}