# CVE-2026-78209: exceljs through 4.4.0 CSV Formula Injection via Unescaped Cell Values

Status: published. Published: 2026-08-24. Updated: 2026-11-08.

exceljs through 4.4.0 fails 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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- exceljs / exceljs (exceljs): ≥ 0; ≤ 4.4.0 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.4 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 8.2 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.41% as of 2026-11-08; percentile 35.52%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-1236

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/exceljs/exceljs (CNA: VulnCheck; product)

- https://github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-9wxc-4rhw-hfrw (CNA: VulnCheck; third-party-advisory, vendor-advisory)

- https://github.com/exceljs/exceljs/blob/v4.4.0/lib/csv/csv.js#L109-L182 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/exceljs-through-csv-formula-injection-via-unescaped-cell-values (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-78209; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-78209; retrieved 2026-11-08; source updated Not reported

Revision: 8f979b1c4881abdc69e642369deeb410acf4f577d88dd28fed6cc19d0fb321b7

Canonical: https://y2.dev/cve/CVE-2026-78209

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