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.

Primary

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.

CSV Injection

Formula Injection

Excel Macro Injection

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.

Confidentiality
Read Application Data
Execute Unauthorized Code or Commands
Low
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.

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

Implementation
When 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).
Moderate
Unfortunately, there is no perfect solution, since different spreadsheet products act differently.

Implementation
If a field starts with a formula character, prepend it with a ' (single apostrophe), which prevents Excel from executing the formula.
Moderate
It is not clear how effective this mitigation is with other spreadsheet software.

Architecture and Design
Certain 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.
Limited
This mitigation has limited effectiveness because it often depends on end users opening spreadsheet software safely.

Hyperlinks or other commands can be executed when a cell begins with the formula identifier, '='

=HYPERLINK(link_location, [friendly_name])

Stripping the leading equals sign, or simply not executing formulas from untrusted sources, impedes malicious activity.

HYPERLINK(link_location, [friendly_name])

CVE-2019-12134
Low privileged user can trigger CSV injection through a contact form field value
https://www.cve.org/CVERecord?id=CVE-2019-12134

CVE-2019-4521
Cloud management product allows arbitrary command execution via CSV injection
https://www.cve.org/CVERecord?id=CVE-2019-4521

CVE-2019-17661
CSV injection in content management system via formula code in a first or last name
https://www.cve.org/CVERecord?id=CVE-2019-17661

Allowed
This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

CWE Content Team
MITRE
2019-11-21
4.0
2020-02-24

CWE Content Team
MITRE
2020-08-20
updated Relationships

CWE Content Team
MITRE
2021-03-15
updated Description, Potential_Mitigations

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated References, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-04-03
4.17
2025-04-03
updated Demonstrative_Examples

CWE Content Team
MITRE
2025-09-09
4.18
2025-09-09
updated References

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Background_Details, Common_Consequences, Description, Detection_Factors, Weakness_Ordinalities