CVE-2026-128339

CVSS 8.7 (high) · published 2026-11-13

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.

Weakness: CWE-770

Source: NVD CVE-2026-128339

References

• https://github.com/exceljs/exceljs
• https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L613-L632
• https://github.com/exceljs/exceljs/blob/v4.4.0/lib/doc/worksheet.js#L895-L901
• https://github.com/exceljs/exceljs/issues/3107
• https://github.com/exceljs/exceljs/pull/3114
• https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-wh3v-83h4-rwwq
• https://www.vulncheck.com/advisories/exceljs-through-4.4.0-memory-exhaustion-via-oversized-merged-cell-range

Check your software

Connect an AI agent to the FixLane MCP server or ask the Telegram bot to check what you have installed against incidents with a verified fixed version.