CVE-2026-78207: exceljs through 4.4.0 Prototype Pollution via deepMerge Reached From Note Serialization
Vendor fix available · Affected: exceljs · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 49% of scored CVEs
DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- exceljs · exceljsup to and including 4.4.0
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- exceljs
- Published
- August 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-78207 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.