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-563: Assignment to Variable without Use

Weakness ID: 563
Abstraction: Variant
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The variable's value is assigned but never used, making it a dead store.
+ Extended Description
After the assignment, the variable is either assigned another value or goes out of scope. It is likely that the variable is simply vestigial, but it is also possible that the unused variable points out a bug.
+ Alternate Terms
Unused Variable
+ 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
ChildOfClassClass710Improper Adherence to Coding Standards
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory1006Bad Coding Practices
+ 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
Implementation
+ 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
Other

Technical Impact: Quality Degradation; Varies by Context

This weakness could be an indication of a bug in the program or a deprecated variable that was not removed and is an indication of poor quality. This could lead to further bugs and the introduction of weaknesses.
+ Demonstrative Examples

Example 1

The following code excerpt assigns to the variable r and then overwrites the value without using it.

(bad code)
Example Language:
r = getName();
r = getNewBuffer(buf);
+ Potential Mitigations

Phase: Implementation

Remove unused variables from the code.
+ 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.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CERT C Secure CodingMSC00-CCompile cleanly at high warning levels
CERT Perl Secure CodingMSC01-PLImpreciseDetect and remove unused variables
Software Fault PatternsSFP2Unused Entities
+ Content History
Submissions
Submission DateSubmitterOrganization
Anonymous Tool Vendor (under NDA)
Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Description, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-05-27CWE Content TeamMITRE
updated Demonstrative_Examples
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-06-27CWE Content TeamMITRE
updated Common_Consequences
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Common_Consequences, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-06-23CWE Content TeamMITRE
updated Common_Consequences, Description, Name, Other_Notes
2014-07-30CWE Content TeamMITRE
updated Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Alternate_Terms, Name, Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2014-06-23Unused Variable
2017-11-08Assignment to Variable without Use ('Unused Variable')

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Page Last Updated: January 18, 2018