CWE-1236: Improper Neutralization of Formula Elements in a CSV File
Official CWE-1236 CWE context with Glexia analysis, remediation guidance, related CVEs, and ATT&CK context.
Glexia's Take
CWE-1236: CSV Injection
Improper Neutralization of Formula Elements in a CSV File represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Confidentiality: Read Application Data,Execute Unauthorized Code or Commands: 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.
Developer Pattern
CWE-1236 is the kind of defect developers can usually prevent with explicit validation, safer framework defaults, and tests that exercise hostile input or unsafe state transitions.
Confidence
high confidence from CWE-1236, 4.20.
Official CWE Definition
CWE-1236: Improper Neutralization of Formula Elements in a CSV File
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.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- Hyperlinks or other commands can be executed when a cell begins with the formula identifier, '=' Stripping the leading equals sign, or simply not executing formulas from untrusted sources, impedes malicious activity.
Remediation
- 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).
- Implementation: If a field starts with a formula character, prepend it with a ' (single apostrophe), which prevents Excel from executing the formula.
- 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.
Detection
- 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.)
Mappings
Related CVEs, CWEs, and ATT&CK context
Related CWEs
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.