CVE-2026-40863: PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-40863 is a high-severity flaw (CVSS 7.5) affecting phpspreadsheet. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 67%)
CISA exploited list	No
Weakness	CWE-770
Published	2026-05-12
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: phpoffice

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-12 22:16 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

phpoffice phpspreadsheet UPGRADE

Affected: < 1.30.4 · >= 2.0.0 and < 2.1.16 · >= 2.2.0 and < 2.4.5 · >= 3.3.0 and < 3.10.5 · >= 4.0.0 and < 5.7.0

Fixed in: 1.30.4, 2.1.16, 2.4.5, 3.10.5, 5.7.0

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy phpspreadsheet || rpm -q phpspreadsheet || phpspreadsheet --version

2. UPGRADE to 1.30.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade phpspreadsheet

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade phpspreadsheet

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison phpspreadsheet sudo apt install phpspreadsheet=<VERSION_BEFORE_2.0.0> sudo apt-mark hold phpspreadsheet

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list phpspreadsheet sudo dnf downgrade phpspreadsheet-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add phpspreadsheet

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40863?

phpspreadsheet: upgrade to 1.30.4, 2.1.16, 2.4.5, 3.10.5, 5.7.0. Exact commands for each OS are on this page.

Is CVE-2026-40863 being exploited?

CVE-2026-40863 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40863 affect?

CVE-2026-40863 affects phpspreadsheet. Severity is high (CVSS 7.5). 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 al

How urgent is CVE-2026-40863?

Priority 45/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-40296 MEDIUM 5.4 UPGRADE PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files
CVE-2026-40902 HIGH 7.5 UPGRADE PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files

References

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