CVE-2026-78209 exceljs through 4.4.0 CSV Formula Injection via Unescaped Cell Values
Attackers can inject malicious formulas into CSV exports via unescaped cell values, leading to data exfiltration or code execution when opened in spreadsheet apps.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-78209?
CVE-2026-78209 is a high-severity vulnerability in exceljs, published on 24 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-1236
Which versions are affected by CVE-2026-78209?
How do I fix CVE-2026-78209?
No fix has been published for CVE-2026-78209 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-78209 being exploited?
There is no known exploitation of CVE-2026-78209 in the wild and no public exploit code.
Sources
Also known as GHSA-4w2g-jrqm-g99q, GHSA-9wxc-4rhw-hfrw.