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CVE-2026-40863

Phpoffice Phpspreadsheet denial of service

7.5 HIGHPublic exploitEPSS 0.49%
  1. Published12 May 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Phpoffice Phpspreadsheet≥ 2.0.0 < 2.1.16 · ≥ 2.2.0 < 2.4.5 · ≥ 3.3.0 < 3.10.5 · ≥ 4.0.0 < 5.7.0

Remediation

Fixed in
Phpoffice Phpspreadsheet≥ 2.1.16

References

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Frequently asked

Is CVE-2026-40863 being actively exploited?

CVE-2026-40863 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.49%.

How severe is CVE-2026-40863?

CVE-2026-40863 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.49% probability of exploitation.

Which products are affected by CVE-2026-40863?

Affected products include Phpoffice Phpspreadsheet.

How do I fix CVE-2026-40863?

Upgrade affected software to a fixed version, for example Phpoffice Phpspreadsheet 2.1.16 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-40863 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.