PhpSpreadsheet vulnerable to XSS in HTML writer via custom number format codes

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Summary

CVECVE-2026-40296
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-06 22:16:25 UTC
Updated2026-05-11 14:42:03 UTC
DescriptionPhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. The HTML writer skips htmlspecialchars escaping when a cell's formatted value differs from the original value. When a cell has a custom number format containing the text placeholder @ along with any additional literal characters (for example ". @", "@ ", or "x@"), the formatter replaces @ with the cell value and adds the extra characters, causing the formatted value to differ from the original and bypassing HTML escaping entirely. An attacker who can control the cell value and number format of an uploaded spreadsheet that is later converted to HTML and displayed to other users can achieve stored cross-site scripting. This issue is fixed in versions 5.7.0, 3.10.5, 2.4.5, 2.1.16, and 1.30.4.

Risk And Classification

Primary CVSS: v3.1 5.4 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS: 0.000350000 probability, percentile 0.105420000 (date 2026-05-12)

Problem Types: CWE-79 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.1CNADECLARED5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Phpoffice Phpspreadsheet All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA PHPOffice PhpSpreadsheet affected >= 4.0.0, <= 5.6.0 Not specified
CNA PHPOffice PhpSpreadsheet affected >= 3.3.0, <= 3.10.4 Not specified
CNA PHPOffice PhpSpreadsheet affected >= 2.2.0, <= 2.4.4 Not specified
CNA PHPOffice PhpSpreadsheet affected >= 2.0.0, <= 2.1.15 Not specified
CNA PHPOffice PhpSpreadsheet affected <= 1.30.3 Not specified

References

ReferenceSourceLinkTags
github.com/PHPOffice/PhpSpreadsheet/security/advisories/GHSA-hrmw-qprp-wgmc 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com Exploit, Mitigation, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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