---
id: "CVE-2026-128338"
page: "https://infrastack.ai/live/CVE-2026-128338"
kind: "vulnerability"
aliases: ["CVE-2026-128338"]
title: "exceljs: crafted spreadsheet column count crashes apps via memory exhaustion"
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: ["denial-of-service", "exceljs", "node", "nodejs", "npm", "package", "spreadsheet-import"]
not_affected_if: ["no-untrusted-xlsx-input", "writes-only"]
published_at: "2026-11-13T10:18:14+00:00"
first_seen_at: "2026-11-13T10:47:34+00:00"
updated_at: "2026-11-13T10:51:12+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-128338", "first_seen_at": "2026-11-13T10:47:34+00:00"}, {"source": "analyst", "url": "https://github.com/exceljs/exceljs/releases", "first_seen_at": "2026-11-13T10:51:12+00:00", "cites": ["https://github.com/exceljs/exceljs/releases"]}]
exploit_sources: []
---

# exceljs: crafted spreadsheet column count crashes apps via memory exhaustion

Link for people: https://infrastack.ai/live/CVE-2026-128338 (this .md is for agents)

exceljs through 4.4.0 trusts the max attribute of a worksheet column element without a bound. A small workbook with a huge max value makes xlsx.load() allocate hundreds of millions of Column objects until the process aborts 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` (and `npm ls exceljs-hardened`): exceljs <= 4.4.0 is affected; exceljs-hardened <= 5.0.2 is affected, 5.1.0 is patched.
- Search for `xlsx.load()`, `readFile()` or streaming readers fed by uploads or imports from outside your team. Apps that only write xlsx files can skip it.
- The crash is a fatal V8 out-of-memory abort, so try/catch does not stop it.

## Fix

No fixed release of upstream exceljs found: the latest release on github.com/exceljs/exceljs/releases is v4.4.0, which is affected. The unofficial fork exceljs-hardened (npm) lists 5.1.0 as patched for the same bug (GHSA-w57r-3mm6-w6g7, affected <= 5.0.2). Until upstream ships a fix, reject untrusted xlsx input or pre-validate it.

## Timeline

- 2026-11-13T10:47:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-128338
- 2026-11-13T10:51:12+00:00 analyst https://github.com/exceljs/exceljs/releases — GHSA-w57r-3mm6-w6g7 is filed on the exceljs-hardened fork (patched 5.1.0), not upstream; upstream latest release is 4.4.0 with no fix seen. Mitigation: size/zip-bomb limits do not help (6 KB file); isolate parsing in a worker with memory limit. No PoC beyond advisory snippet, no exploitation reported. Not marked verified: upstream fix status is inferred from the releases page.

## Documents

- [advisory] Vendor advisory: github.com https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-w57r-3mm6-w6g7
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/exceljs-through-4.4.0-memory-exhaustion-via-unbounded-worksheet-column-range
- [fix] exceljs releases (latest v4.4.0) https://github.com/exceljs/exceljs/releases

## From the sources

exceljs through 4.4.0 contains a memory exhaustion vulnerability that allows attackers to crash applications by supplying a worksheet col element with an unbounded max attribute. Attackers can craft a small workbook with a huge max value, causing xlsx.load() to allocate hundreds of millions of Column objects and abort the process with an uncatchable heap out-of-memory error.

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