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Vulnerability record

CVE-2026-128339

highCVSS 4.0 8.7Published · exceljs

The short answer

CVE-2026-128339 affects exceljs exceljs and is rated high (CVSS 8.7). It is not in CISA's Known Exploited Vulnerabilities catalog.

What it is

ExcelJS through 4.4.0 contains a memory exhaustion vulnerability in Worksheet._parseMergeCells that allows attackers to crash applications by supplying unbounded mergeCell ranges. Attackers can craft a small workbook with a mergeCell ref like A1:XFD1048576, causing xlsx.load() to create billions of Row and Cell objects and abort the process.

Weakness: CWE-770.

Severity

8.7 high

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Exploited (CISA KEV)

Not listed

CISA lists confirmed exploitation only

EPSS, next 30 days

No score

FIRST scores CVEs within a day of publication

How it can be exploited

Attack vector
Network
Attack complexity
Low
Attack requirements
None
Privileges required
None
User interaction
None
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Affected products

exceljs. NVD's record lists the exact affected versions.

References

Questions

Is CVE-2026-128339 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog as of 2026-11-13.

How do I fix CVE-2026-128339?

Follow the vendor advisory in the references below. NVD lists the affected versions under its configurations.

From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Received. The description is NVD's text, quoted as published.

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