CWE

Reliance on File Name or Extension of Externally-Supplied File

ID: 646		Date: (C)2012-05-14   (M)2022-10-10
Type: weakness		Status: INCOMPLETE
Abstraction Type: Variant

Description

The software allows a file to be uploaded, but it relies on the file name or extension of the file to determine the appropriate behaviors. This could be used by attackers to cause the file to be misclassified and processed in a dangerous fashion.

Extended Description

An application might use the file name or extension of of a user-supplied file to determine the proper course of action, such as selecting the correct process to which control should be passed, deciding what data should be made available, or what resources should be allocated. If the attacker can cause the code to misclassify the supplied file, then the wrong action could occur. For example, an attacker could supply a file that ends in a ".php.gif" extension that appears to be a GIF image, but would be processed as PHP code. In extreme cases, code execution is possible, but the attacker could also cause exhaustion of resources, denial of service, exposure of debug or system data (including application source code), or being bound to a particular server side process. This weakness may be due to a vulnerability in any of the technologies used by the web and application servers, due to misconfiguration, or resultant from another flaw in the application itself.

Enabling Factors for Exploitation
There is reliance on file name and/or file extension on the server side for processing.

Likelihood of Exploit: High

Applicable Platforms
Language Class: Language-independent

Time Of Introduction

• Architecture and Design
• Implementation
• Operation

Related Attack Patterns

• CAPEC-209

Common Consequences

Scope	Technical Impact	Notes
Confidentiality	Read application data	An attacker may be able to read sensitive data.
Availability	DoS: crash / exit / restart	An attacker may be able to cause a denial of service.
Access_Control	Gain privileges / assume identity	An attacker may be able to gain privileges.

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description	Effectiveness	Notes
Architecture and Design		Make decisions on the server side based on file content and not on file name or extension.

Relationships

Related CWE	Type	View	Chain
CWE-646 ChildOf CWE-896	Category	CWE-888

Demonstrative Examples
None

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings
None

References:
None