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Not in CISA KEV
HIGH severity

CVE-2026-128340 — Exceljs

HIGH

CVE-2026-128340 is a high-severity (CVSS 7.5) CWE-770 vulnerability. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

ExcelJS through 4.4.0 contains a memory exhaustion vulnerability that allows attackers to crash applications by supplying a workbook with an oversized defined-name range. DefinedNames.addEx…

Published
Updated
Affected
—
Patched
—
Exploits
None indexed
Exploitation data as of Nov 13, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs51th percentile — riskier than 51% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Description

ExcelJS through 4.4.0 contains a memory exhaustion vulnerability that allows attackers to crash applications by supplying a workbook with an oversized defined-name range. DefinedNames.addEx expands ranges such as S!$A$1:$XFD$1048576 from xl/workbook.xml cell by cell, causing an uncatchable fatal heap out-of-memory error during xlsx.load().

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    The records we use list no fixed release for CVE-2026-128340. Check the upstream advisory for a patched version, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

ExcelJS through 4.4.0 contains a memory exhaustion vulnerability that allows attackers to crash applications by supplying a workbook with an oversized defined-name range. DefinedNames.addEx expands ranges such as S!$A$1:$XFD$1048576 from xl/workbook.xml cell by cell, causing an uncatchable fatal heap out-of-memory error during xlsx.load().
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