CVE-2026-40863: Phpoffice Phpspreadsheet

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. Prior to 1.30.4, 2.1.16, 2.4.5, 3.10.5, and 5.7.0, 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 attempt to iterate ~1 billion rows, causing CPU exhaustion and denial of service. This vulnerability is fixed in 1.30.4, 2.1.16, 2.4.5, 3.10.5, and 5.7.0.

Affected products

• Phpoffice Phpspreadsheet: before 1.30.4 (fixed in 1.30.4); from 2.0.0, before 2.1.16 (fixed in 2.1.16); from 2.2.0, before 2.4.5 (fixed in 2.4.5); from 3.3.0, before 3.10.5 (fixed in 3.10.5); from 4.0.0, before 5.7.0 (fixed in 5.7.0)

Published 2026-05-12. Last modified 2026-06-17.