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 ('Unused Variable')

Weakness ID: 563
Abstraction: Variant
Status: Draft
Presentation Filter:
+ Description

Description Summary

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.

+ Time of Introduction
  • Implementation
+ Common Consequences
ScopeEffect
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.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class398Indicator of Poor Code Quality
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory747CERT C Secure Coding Section 49 - Miscellaneous (MSC)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory883CERT C++ Secure Coding Section 49 - Miscellaneous (MSC)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory886SFP Primary Cluster: Unused entities
Software Fault Pattern (SFP) Clusters (primary)888
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
Anonymous Tool Vendor (under NDA)
CERT C Secure CodingMSC00-CCompile cleanly at high warning levels
CERT C++ Secure CodingMSC00-CPPCompile cleanly at high warning levels
Software Fault PatternsSFP2Unused Entities
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
Anonymous Tool Vendor (under NDA)Externally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Description, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative_Examples
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Common_Consequences, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-06-23CWE Content TeamMITREInternal
updated Common_Consequences, Description, Name, Other_Notes
2014-07-30CWE Content TeamMITREInternal
updated Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2014-06-23Unused Variable

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Page Last Updated: January 11, 2017