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CVE-2026-128342

7.5, high

ExcelJS through 4.4.0 contains a denial of service vulnerability that allows attackers to block the event loop by supplying an unbounded…

NVD (opens in a new tab) CVE.org (opens in a new tab)
CVSS
7.5, high high CVSS v3.1
EPSS, next 30 days
0.6% higher than 50.7% of scored CVEs
Exploitation
No public evidence
Published
13 Nov 2026yesterday

Description

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.

Details

Vendor
Exceljs
Product
exceljs
Weakness
CWE-606 (opens in a new tab)
Status
Awaiting analysis
Updated
13 Nov 2026
Assigner
disclosure@vulncheck.com

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

References 5

Advisories 1

Other references 4

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Exceljs CVEs

Every Exceljs CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-128337 exceljs Prototype Pollution Vulnerability EPSS 0.4% 7, high
  • CVE-2026-128338 exceljs Allocation of Resources Without Limits or Throttling Vulnerability EPSS 0.6% 7.5, high
  • CVE-2026-128341 exceljs Allocation of Resources Without Limits or Throttling Vulnerability EPSS 0.6% 7.5, high
  • CVE-2026-128346 ExcelJS through 4.4.0 contains a resource leak vulnerability in the streaming WorkbookReader.parse that leaves temporary files and open… EPSS 0.6% 7.5, high

Beyond this page

Is CVE-2026-128342 in your network?

This page tells you how dangerous CVE-2026-128342 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

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Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 14 Nov 2026, not the live upstream state.