CVE-2026-40296

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

Published May 6, 2026 CVSS 3.1 · 5.4 Medium EPSS < 1% KEV · Not listed
Description
PhpSpreadsheet 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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-hrmw-qprp-wgmc PhpSpreadsheet has XSS via number format code with @ text placeholder bypasses htmlspecialchars in HTML writer
History
Type Values Removed Values Added
CPEs cpe:2.3:a:phpoffice:phpspreadsheet:*:*:*:*:*:*:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Phpoffice
Phpoffice phpspreadsheet
Vendors & Products Phpoffice
Phpoffice phpspreadsheet
Type Values Removed Values Added
Description PhpSpreadsheet 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.
Title PhpSpreadsheet vulnerable to XSS in HTML writer via custom number format codes
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 7, 2026, 2:03 PM
Reserved
Apr 10, 2026, 8:22 PM
Status
Analyzed
Published
May 6, 2026, 10:16 PM
Modified
Oct 26, 2026, 7:10 PM