CVE-2026-78207
CRITICAL9.4CVSS v3
—CVSS v2
0.44%
EPSS (exploit probability)
CWE-1321CWE
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.
CVSS v3 vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Affected routers (0)
No routers currently mapped to this CVE in our database.