CVE-2026-78209Public exploit

Formula execution via unescaped CSV cell values

Published Aug 24, 2026 · Updated Aug 24, 2026

CSV formula injection in ExcelJS 4.4.0 and earlier allows attackers to create executable formulas through exported cell values. The default mapper in lib/csv/csv.js passes strings beginning with =, +, -, @, tab, or carriage return directly to fast-csv without forcing text treatment. Exploitation requires control of an exported value and a recipient opening the CSV in a spreadsheet; resulting formulas can send data or invoke supported external actions.

CVSS severityUnavailable
Unscored
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSV formula injection in ExcelJS 4.4.0 and earlier allows attackers to create executable formulas through exported cell values. The default mapper in lib/csv/csv.js passes strings beginning with =, +, -, @, tab, or carriage return directly to fast-csv without forcing text treatment. Exploitation requires control of an exported value and a recipient opening the CSV in a spreadsheet; resulting formulas can send data or invoke supported external actions.

The record

CVE
CVE-2026-78209
Published
Aug 24, 2026
Updated
Aug 24, 2026
Vendor
ExcelJS
Product
ExcelJS
Classifications
T1204.002
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Aug 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=4.4.0

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

ExcelJS · ExcelJSversion=0 <=4.4.0

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1204.002User Execution: Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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