CVE-2026-128342

CVSS 8.7 (high) · published 2026-11-13

ExcelJS through 4.4.0 contains a denial of service vulnerability that allows attackers to block the event loop by supplying an unbounded sheetId in xl/workbook.xml. Attackers can provide a workbook with a huge sheetId, making the sparse worksheet array walk stall worksheets, getWorksheet and writeBuffer for seconds.

Weakness: CWE-606

Source: NVD CVE-2026-128342

References

• https://github.com/exceljs/exceljs
• https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/workbook.js#L119-L125
• https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/workbook.js#L200-L206
• https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-9vv6-5g3h-prg5
• https://www.vulncheck.com/advisories/exceljs-through-4.4.0-denial-of-service-via-oversized-worksheet-sheetid

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