---
id: "CVE-2026-128341"
page: "https://infrastack.ai/live/CVE-2026-128341"
kind: "vulnerability"
aliases: ["CVE-2026-128341"]
title: "ExcelJS: crafted workbook exhausts CPU and memory, crashing Node processes"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "exceljs", "fixed": [], "affected": "<= 4.4.0", "ecosystem": "npm"}, {"name": "exceljs-hardened", "fixed": ["5.1.0"], "affected": "<= 5.0.2", "ecosystem": "npm"}]
ecosystems: []
tags: ["exceljs", "exceljs-hardened", "javascript", "node", "npm", "package"]
not_affected_if: ["export-only", "no-untrusted-xlsx-input"]
published_at: "2026-11-13T10:18:14+00:00"
first_seen_at: "2026-11-13T10:47:34+00:00"
updated_at: "2026-11-13T10:51:10+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-128341", "first_seen_at": "2026-11-13T10:47:34+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-11-13T10:51:10+00:00"}]
exploit_sources: []
---

# ExcelJS: crafted workbook exhausts CPU and memory, crashing Node processes

Link for people: https://infrastack.ai/live/CVE-2026-128341 (this .md is for agents)

ExcelJS through 4.4.0 parses unbounded sqref ranges in data-validations-xform.js without limits. A small crafted .xlsx file makes xlsx.load() iterate billions of cell addresses, blocking the event loop and crashing the process with an out-of-memory error.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- npm:exceljs affected <= 4.4.0 fixed no fixed version listed
- npm:exceljs-hardened affected <= 5.0.2 fixed 5.1.0

## How to check

- Run `npm ls exceljs`; exceljs <= 4.4.0 is affected per VulnCheck (4.4.0 reproduced in exceljs issue #3093).
- If you use the fork, run `npm ls exceljs-hardened`; versions <= 5.0.2 are affected, 5.1.0 fixes it.
- Find calls to `workbook.xlsx.load()` or `readFile()` on files from uploads, email or other outside sources.

## Fix

No fixed release of upstream exceljs found (latest 4.4.0). The unofficial fork exceljs-hardened fixes it in 5.1.0 (<= 5.0.2 affected). Until upstream ships a fix, reject untrusted .xlsx input or pre-check sheet XML dataValidation sqref sizes before calling load().

## Timeline

- 2026-11-13T10:47:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-128341
- 2026-11-13T10:51:10+00:00 analyst — GHSA-f689-fh93-2pm2 is published in the third-party fork exceljs-hardened (affected <=5.0.2, patched 5.1.0), not by upstream exceljs. Upstream exceljs 4.4.0 reproduced in issue #3093 (open, PRs #3096/#3103 referenced; no merged fix or release seen). No upstream fixed version found, so fix left unconfirmed and nothing marked verified.

## Documents

- [advisory] Vendor advisory: github.com https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-f689-fh93-2pm2
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/exceljs-through-4.4.0-denial-of-service-via-oversized-data-validation-sqref
- [discussion] exceljs#3093: crafted dataValidation sqref causes unbounded CPU/memory (DoS) https://github.com/exceljs/exceljs/issues/3093

## From the sources

ExcelJS through 4.4.0 contains a resource exhaustion vulnerability in data-validations-xform.js that allows attackers to exhaust CPU and memory by supplying unbounded sqref ranges. Attackers can provide a small crafted workbook with a sqref of A1:XFD1048576 to make xlsx.load() iterate billions of addresses, blocking the event loop and crashing the process with an uncatchable out-of-memory error.

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