PhpSpreadsheet has CPU Denial of Service via Unbounded Row Number in XLSX Row Dimensions — CVE-2026-40902

Summary

## 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…

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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