CVE-2021-28931: Forkcms/forkcms Arbitrary File Upload Vulnerability

HIGH
Advisory Identifier: GHSA-748f-wv76-x9hg
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CVSS 8.8
CWE-434
Published
Advisory Summary

CVE-2021-28931 is a HIGH (CVSS 8.8) arbitrary file upload vulnerability (CWE-434: Unrestricted Upload of File with Dangerous Type) affecting Forkcms/forkcms libraries in the Packagist ecosystem. The issue involves arbitrary file upload in fork cms. Remediation is available by upgrading affected packages to version 5.9.3.

CVE-2021-28931 at a Glance

CVE Identifier CVE-2021-28931
GHSA Identifier GHSA-748f-wv76-x9hg
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-434: Unrestricted Upload of File with Dangerous Type
Affected Product Forkcms/forkcms
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 8.8

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:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
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-2021-28931

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

forkcms/forkcms fixed: 5.9.3 
Upgrade forkcms/forkcms to 5.9.3
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 forkcms/forkcms

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-28931, inspect your project dependencies for Forkcms/forkcms:

inspect dependencies for forkcms/forkcms

Analyze the terminal output to locate any version of Forkcms/forkcms in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.9.3), 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-434: Unrestricted Upload of File with Dangerous Type, where the product allows the upload or transfer of dangerous file types that are automatically processed within its environment. In Forkcms/forkcms, 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

Arbitrary file upload vulnerability in Fork CMS 5.9.2 allows attackers to create or replace arbitrary files in the /themes directory via a crafted zip file uploaded to the Themes panel.

CVE-2021-28931 Affected Forkcms/forkcms Versions

1 component(s)
Fixed Versions:
5.9.3
Product / Package Ecosystem Affected Versions Fixed Version
forkcms/forkcms
 Packagist
< 5.9.3
5.9.3

References

NVD — CVE-2021-28931 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-28931
Forkcms/forkcms Source Repository REPOSITORY
https://github.com/forkcms/forkcms/pull/3351
Forkcms/forkcms Source Repository REPOSITORY
https://github.com/bousalman/ForkCMS-arbitrary-upload/blob/main/README.md
Forkcms/forkcms Release RELEASE
https://github.com/forkcms/forkcms/releases/tag/5.9.2

Frequently Asked Questions

What is CVE-2021-28931?
CVE-2021-28931 is a security vulnerability in Forkcms/forkcms involving Arbitrary file upload in Fork CMS under CWE-434: Unrestricted Upload of File with Dangerous Type.
Which Forkcms/forkcms versions are affected?
Affected versions include releases prior to 5.9.3 across affected packages: forkcms/forkcms.
What version fixes CVE-2021-28931?
Upgrading to 5.9.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is forkcms/forkcms affected?
Yes, forkcms/forkcms is affected in releases prior to 5.9.3. Upgrade your dependency to 5.9.3 or later.
What is the CVSS score of CVE-2021-28931?
CVE-2021-28931 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-28931?
CVE-2021-28931 is classified under CWE-434: Unrestricted Upload of File with Dangerous Type (The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.).
How can I check Packagist dependencies for CVE-2021-28931?
Run the dependency tree command: 'inspect dependencies for forkcms/forkcms'. 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-748f-wv76-x9hg",
  "modified" : "2021-07-13T15:53:15Z",
  "published" : "2021-09-08T17:26:26Z",
  "aliases" : [ "CVE-2021-28931" ],
  "summary" : "Arbitrary file upload in Fork CMS",
  "details" : "Arbitrary file upload vulnerability in Fork CMS 5.9.2 allows attackers to create or replace arbitrary files in the /themes directory via a crafted zip file uploaded to the Themes panel.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "forkcms/forkcms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.9.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.9.2"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-28931"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/forkcms/forkcms/pull/3351"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bousalman/ForkCMS-arbitrary-upload/blob/main/README.md"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/forkcms/forkcms/releases/tag/5.9.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-434" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-07-08T13:59:31Z",
    "nvd_published_at" : "2021-07-07T15:15:00Z"
  }
}