Is CVE-2026-40863 actively exploited?

No active exploitation of CVE-2026-40863 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-40863 be exploited remotely?

Yes. CVE-2026-40863 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-40863?

CVE-2026-40863 has a CVSS score of 7.5 (HIGH).

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HIGH

CVE-2026-40863

CWE-770Published: May 12, 2026· Updated: May 13, 2026

7.5

CVSS v3.1

EPSS:0.04%probability of exploitation in 30 daysPercentile:12.8th

Official Description

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.

NVD Source

Technical Analysis

CVE-2026-40863 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 7.5.