---
id: "CVE-2026-128345"
page: "https://infrastack.ai/live/CVE-2026-128345"
kind: "vulnerability"
aliases: ["CVE-2026-128345"]
title: "ExcelJS: crafted spreadsheet formulas can freeze Node.js servers"
severity: "medium"
cvss: 6.9
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["exceljs", "node.js", "npm", "package"]
not_affected_if: ["no-untrusted-xlsx-input"]
published_at: "2026-11-13T10:18:15+00:00"
first_seen_at: "2026-11-13T10:47:35+00:00"
updated_at: "2026-11-13T10:54:30+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-128345", "first_seen_at": "2026-11-13T10:47:35+00:00"}]
exploit_sources: []
---

# ExcelJS: crafted spreadsheet formulas can freeze Node.js servers

Link for people: https://infrastack.ai/live/CVE-2026-128345 (this .md is for agents)

ExcelJS through 4.4.0 has a regular expression flaw in its shared formula handling that backtracks heavily on long formulas. A crafted spreadsheet can block the Node.js event loop and stall the process.

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

## How to check

- Check the installed ExcelJS version with `npm ls exceljs`
- Look for ExcelJS reading uploaded or untrusted .xlsx files in your code

## Timeline

- 2026-11-13T10:47:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-128345

## Documents

- [advisory] Vendor advisory: github.com https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-pr65-54q8-vhqm
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/exceljs-through-4.4.0-redos-via-slideformula-shared-formula-translation

## From the sources

ExcelJS through 4.4.0 contains a regular expression denial of service vulnerability in slideFormula in lib/utils/shared-formula.js when translating shared formulas to child cells. Attackers can supply a crafted spreadsheet with very long master formulas, such as runs of hyphens, causing quadratic regex backtracking that blocks the Node.js event loop.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_