Is there a public exploit for CVE-2026-128336?

No public exploit for CVE-2026-128336 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-128336?

CVE-2026-128336 scores CVSS 6.3 (v4.0), rated medium.

What does CVE-2026-128336 affect?

CVE-2026-128336 affects exceljs exceljs.

6.3 Medium

ExcelJS through 4.4.0 contains a prototype pollution vulnerability that allows attackers to add numeric keys to Object.prototype through a…

CVE-2026-128336

ExcelJS through 4.4.0 contains a prototype pollution vulnerability that allows attackers to add numeric keys to Object.prototype through a crafted defined name referencing a proto sheet. Attackers can supply an xlsx whose xl/workbook.xml definedName range targets proto, causing CellMatrix to write empty arrays onto Object.prototype process-wide when workbook.xlsx.load() runs.

Assessment

CVSS: 6.3 (v4.0)
Severity: Medium
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 13 November 2026
Last updated: 13 November 2026
Affected: exceljs · exceljs
Assigner: VulnCheck

CVSS vectorCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

At the source

EUVD (ENISA)

References

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