CVE-2026-40863 | PhpSpreadsheet: CPU Denial of Service via Unbounded Row Index in SpreadsheetML XML Reader

Exp

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.

Published: 2026-05-12 Last update: 2026-05-13 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-40863 is rated Exploit Available (51/100): CVSS High severity, with low exploitation likelihood (EPSS 0.06%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-40863

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-40863

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-18 0.04% 0.06% +0.02%
2 2026-05-13 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-40863

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-40863

GitHub Security Advisory for CVE-2026-40863

GHSA-84wq-86v6-x5j6 · Severity: high · Ecosystem: composer — PhpSpreadsheet has CPU Denial of Service via Unbounded Row Index in SpreadsheetML XML Reader

Affected software / configurations for CVE-2026-40863

Vendor Product Version Raw CPE
phpoffice phpspreadsheet < 1.30.4 cpe:2.3:a:phpoffice:phpspreadsheet:*:*:*:*:*:*:*:*
phpoffice phpspreadsheet >= 2.0.0, < 2.1.16 cpe:2.3:a:phpoffice:phpspreadsheet:*:*:*:*:*:*:*:*
phpoffice phpspreadsheet >= 2.2.0, < 2.4.5 cpe:2.3:a:phpoffice:phpspreadsheet:*:*:*:*:*:*:*:*
phpoffice phpspreadsheet >= 3.3.0, < 3.10.5 cpe:2.3:a:phpoffice:phpspreadsheet:*:*:*:*:*:*:*:*
phpoffice phpspreadsheet >= 4.0.0, < 5.7.0 cpe:2.3:a:phpoffice:phpspreadsheet:*:*:*:*:*:*:*:*

References for CVE-2026-40863

cvelogic Threat Intelligence