CVE-2026-128337

HighCVSS 7.0/10Last modified Nov 13, 2026

Description

ExcelJS through 4.4.0 contains a prototype pollution vulnerability in mergeConditionalFormattings that allows attackers to modify Object.prototype by supplying an x14:cfRule id of __proto__. Attackers can craft an xlsx file that, when loaded with xlsx.load(), sets properties such as type, direction, border and cfvo on every object in the process until it restarts.

Metrics

CVSS 3.1 7.0/10CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L

Weakness enumeration

CWE-1321

Affected software

Source: the vendor's advisory (CNA). NVD analysis pending.

No affected versions have been published.

Timeline

Published
Nov 13, 2026
Last modified
Nov 13, 2026
NVD status
Awaiting Analysis

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CVE-2026-128337: High severity, CVSS 7.0 | Vulnix