CVE-2026-78209
CSV formula-injection in exceljs-hardened allows code/data exfiltration when opened
Is CVE-2026-78209 being exploited?
Not confirmed. CVE-2026-78209 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.29% probability of exploitation in the next 30 days.
How severe is CVE-2026-78209?
CVE-2026-78209 is rated High with a CVSS score of 8.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-78209?
Yes. A fix has been recorded for CVE-2026-78209. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-78209 affect?
CVE-2026-78209 affects exceljs-hardened <5.0.0, Node.js apps using exceljs-hardened for CSV export, Any service exporting user-controlled CSVs. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-78209?
Upgrade to exceljs-hardened 5.0.0+ or sanitize leading =,+,-,@ in CSV exports
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker-controlled cell values can inject spreadsheet formulas in CSVs; opening the file can exfiltrate data or trigger commands via spreadsheet functions.
Immediate action required
- affected<= 4.4.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.