CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-646: Reliance on File Name or Extension of Externally-Supplied File

Weakness ID: 646
Abstraction: Variant
Structure: Simple
Status: Incomplete
Presentation Filter:
+ 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.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
NatureTypeIDName
ChildOfClassClass345Insufficient Verification of Data Authenticity
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory442Web Problems
ChildOfClassClass345Insufficient Verification of Data Authenticity
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
Implementation
Operation
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

(Language-Independent classes): (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Confidentiality

Technical Impact: Read Application Data

An attacker may be able to read sensitive data.
Availability

Technical Impact: DoS: Crash, Exit, or Restart

An attacker may be able to cause a denial of service.
Access Control

Technical Impact: Gain Privileges or Assume Identity

An attacker may be able to gain privileges.
+ Likelihood Of Exploit
High
+ Potential Mitigations

Phase: Architecture and Design

Make decisions on the server side based on file content and not on file name or extension.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
NatureTypeIDName
MemberOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
2008-01-30Evgeny LebanidzeCigital
Modifications
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITRE
updated Common_Consequences, Relationships, Observed_Example
2008-10-13CWE Content TeamMITRE
Significant clarification of the weakness description.
2008-10-14CWE Content TeamMITRE
updated Description, Name, Observed_Examples, Relationships
2009-07-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2009-10-29CWE Content TeamMITRE
updated Common_Consequences
2010-12-13CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences
2011-03-29CWE Content TeamMITRE
updated Common_Consequences, Description
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Enabling_Factors_for_Exploitation
Previous Entry Names
Change DatePrevious Entry Name
2008-10-14Taking Actions based on File Name or Extension of a User Supplied File

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Page Last Updated: November 14, 2017