CVE-2026-78209

Summary

exceljs-hardened versions before 5.0.0 fail to neutralize leading equals, plus, minus, or at signs in cell values written to CSV output. Attackers who can influence exported cell values can inject formulas that execute when the CSV file is opened in a spreadsheet application, potentially exfiltrating data or performing other malicious actions.

Affected Software

Weaknesses

• CWE-1236: Improper Neutralization of Formula Elements in a CSV File

References

• https://github.com/exceljs/exceljs
• https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-9wxc-4rhw-hfrw
• https://github.com/exceljs/exceljs/blob/v4.4.0/lib/csv/csv.js#L109-L182
• https://www.vulncheck.com/advisories/exceljs-through-csv-formula-injection-via-unescaped-cell-values

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