CVE-2026-78207EPSS p47.0%

CVE-2026-78207CVE-2026-78207

Description

exceljs through 4.4.0 contains a prototype pollution vulnerability in the deepMerge helper that fails to reject __proto__, constructor, or prototype keys when merging note objects. Attackers can assign parsed JSON with a malicious __proto__ property to cell notes, modifying Object.prototype and affecting all plain objects created in the process.

Scoring

CVSS 9.4 ()
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
EPSS0.60% probability of exploitation · percentile 47.0% · 2026-10-05T12:00:23Z
Last modified2026-08-31
Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.