CVE-2026-128339
Received Received - Intake

Memory Exhaustion in ExcelJS via Unbounded MergeCell Ranges

Publication date: 2026-11-13

Last updated on: 2026-11-13

Assigner: VulnCheck

Description
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.

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Meta Information

Published
2026-11-13
Last Modified
2026-11-13
Generated
2026-11-13
AI Q&A
2026-11-13
EPSS Evaluated
N/A
NVD
CVE-2026-128339
EUVD
EUVD-2026-125038

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
exceljs exceljs From 0 (inc) to 4.4.0 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

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Executive Summary

This vulnerability is a memory exhaustion issue in ExcelJS versions up to 4.4.0. It occurs when processing a maliciously crafted Excel file with an oversized merged cell range like A1:XFD1048576. The library attempts to create billions of Row and Cell objects for the entire range, consuming excessive memory and crashing the application.

Detection Guidance

To detect this vulnerability, monitor for crashes in applications using ExcelJS when processing Excel files. Check for heap out-of-memory errors in logs. Use tools like Node.js process monitors to track memory usage spikes during file parsing.

Impact Analysis

This vulnerability can crash applications processing Excel files, leading to denial-of-service. Attackers can remotely trigger crashes with small malicious files, causing unavailability of services relying on ExcelJS. The impact is severe as the crash cannot be caught or handled gracefully.

Mitigation Strategies

Upgrade ExcelJS to a patched version (e.g., 4.4.1 or later) that includes row number validation and merge range limits. If upgrading is not possible, implement input validation to reject excessively large merge ranges before processing.

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