Official definition

The product saves user-provided information into a Comma-Separated Value (CSV) file, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as a command when the file is opened by a spreadsheet product.

User-provided data is often saved to traditional databases. This data can be exported to a CSV file, which allows users to read the data using spreadsheet software such as Excel, Numbers, or Calc. This software interprets entries beginning with '=' as formulas, which are then executed by the spreadsheet software. The software's formula language often allows methods to access hyperlinks or the local command line, and frequently allows enough characters to invoke an entire script.

Characteristics

Alternate terms

CSV Injection
Formula Injection
Excel Macro Injection

Modes of introduction

Implementation: The weakness is in the implementation of a software's CSV export feature, in particular how it formats formula entries as the output gets flattened into a text file.

Common consequences

Impact	Scope	Explanation
Read Application Data, Execute Unauthorized Code or Commands	Confidentiality	Attackers can populate data fields which, when saved to a CSV file, may attempt information exfiltration or other malicious activity when automatically executed by the spreadsheet software. Note that current versions of Excel warn users of untrusted content.

Risk mitigations

Implementation · Effectiveness: ModerateWhen generating CSV output, ensure that formula-sensitive metacharacters are effectively escaped or removed from all data before storage in the resultant CSV. Risky characters include '=' (equal), '+' (plus), '-' (minus), and '@' (at).Unfortunately, there is no perfect solution, since different spreadsheet products act differently.
Implementation · Effectiveness: ModerateIf a field starts with a formula character, prepend it with a ' (single apostrophe), which prevents Excel from executing the formula.It is not clear how effective this mitigation is with other spreadsheet software.
Architecture and Design · Effectiveness: LimitedCertain implementations of spreadsheet software might disallow formulas from executing if the file is untrusted, or if the file is not authored by the current user.This mitigation has limited effectiveness because it often depends on end users opening spreadsheet software safely.

Detection methods

Method	Approach	Effectiveness
Automated Static Analysis	Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)	High

Representative vulnerabilities

Below are representative vulnerabilities related to this CWE, prioritized by severity.

Sources (2)

MITRE CWE

CWE Terms of Use

CWE-1236: Improper Neutralization of Formula Elements in a CSV File

What is CWE-1236?

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Vulnerabilities mapped to CWE-1236

No data

Official definition

Characteristics

Alternate terms

Modes of introduction

Common consequences

Risk mitigations

Detection methods

Representative vulnerabilities

Supporting documents

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