PhpSpreadsheet has CPU Denial of Service via Unbounded Row Index in SpreadsheetML XML Reader — CVE-2026-40863

Summary

## 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 `<Row>` element, which inflates the internal `cachedHighestRow` to ~1 billion. Any subsequent call to `getRowIterator()` without an explicit end row will…

Product

composer: phpoffice/phpspreadsheet

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

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