CVE-2026-78209
CVE-2026-78209
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (33.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 33.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Weakness classification (CWE)
References
- github.com/exceljs/exceljs (product)
- github.com/mateocallec/exceljs-hardened/security/advisories/GHSA-9wxc-4rhw-hfrw (third-party-advisory)
- github.com/exceljs/exceljs/blob/v4.4.0/lib/csv/csv.js (technical-description)
- www.vulncheck.com/advisories/exceljs-through-csv-formula-injection-via-unescape… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-78209?
- CVE-2026-78209 is a high-severity vulnerability, classified under Improper Neutralization of Formula Elements in a CSV File. CVSS score: 8.2/10. Published 2026-08-24.
- How severe is CVE-2026-78209?
- High severity. CVSS v3 base score is 8.2 out of 10.