Vulnerability in phpoffice/phpspreadsheet (CVE-2026-40863)
Summary
Vulnerability in phpoffice/phpspreadsheet (CVE-2026-40863). Risk of unauthorized operations or information disclosure. Exploitable via cachedHighestRow. Mitigation: upgrade to 1.30.4 or later.
Original description
The description as published by the source.
Summary
The 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 `` 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.
Details
In src/PhpSpreadsheet/Reader/Xml.php, the loadSpreadsheetFromFile method processes `` elements:
// Xml.php:397-402
if (isset($row_ss['Index'])) {
$rowID = (int) $row_ss['Index']; // No validation against MAX_ROW
}
if (isset($row_ss['Hidden'])) {
$rowVisible = ((string) $row_ss['Hidden']) !== '1';
$spreadsheet->getActiveSheet()->getRowDimension($rowID)->setVisible($rowVisible);
}
The $rowID value read from ss:Index is cast to int with no upper bound check. It is then passed to getRowDimension():
// Worksheet.php:1342-1351
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];
}
This inflates cachedHighestRow to the attacker-controlled value. Additionally, at line 412, $cellRange = $columnID . $rowID is construc…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-40863 has been found in phpoffice/phpspreadsheet.
Attackers can target a specific entry point like cachedHighestRow over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade phpoffice/phpspreadsheet to 1.30.4 or later.
If unsure, ask your IT team or search "phpoffice/phpspreadsheet CVE-2026-40863" on the vendor's site.
CVE-2026-40863 (phpoffice/phpspreadsheet) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: cachedHighestRow / loadSpreadsheetFromFile / RowIterator / DefaultReadFilter
Patched: 1.30.4 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-400) exists in phpoffice/phpspreadsheet. Attackers reach the vulnerable code path via cachedHighestRow without authentication.
Check the vendor advisory for the affected versions of phpoffice/phpspreadsheet. Attack surface: cachedHighestRow / loadSpreadsheetFromFile / RowIterator / DefaultReadFilter.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.30.4.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'phpoffice/phpspreadsheet' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'phpoffice/phpspreadsheet' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
phpoffice/phpspreadsheetを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade phpoffice/phpspreadsheet to 1.30.4ステージング環境で 1.30.4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com