Common Weakness Enumeration

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CWE-462: Duplicate Key in Associative List (Alist)

Weakness ID: 462
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

Duplicate keys in associative lists can lead to non-unique keys being mistaken for an error.

Extended Description

A duplicate key entry -- if the alist is designed properly -- could be used as a constant time replace function. However, duplicate key entries could be inserted by mistake. Because of this ambiguity, duplicate key entries in an association list are not recommended and should not be allowed.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms






+ Common Consequences

Technical Impact: Quality degradation; Varies by context

+ Likelihood of Exploit


+ Demonstrative Examples

Example 1

The following code adds data to a list and then attempts to sort the data.

(Bad Code)
alist = []
while (foo()): #now assume there is a string data with a key basename

Since basename is not necessarily unique, this may not sort how one would like it to be.

+ Potential Mitigations

Phase: Architecture and Design

Use a hash table instead of an alist.

Phase: Architecture and Design

Use an alist which checks the uniqueness of hash keys with each entry before inserting the entry.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory461Data Structure Issues
Development Concepts (primary)699
ChildOfWeakness BaseWeakness Base694Use of Multiple Resources with Duplicate Identifier
Research Concepts (primary)1000
ChildOfCategoryCategory744CERT C Secure Coding Section 10 - Environment (ENV)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory878CERT C++ Secure Coding Section 10 - Environment (ENV)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory977SFP Secondary Cluster: Design
Software Fault Pattern (SFP) Clusters (primary)888
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPDuplicate key in associative list (alist)
CERT C Secure CodingENV02-CBeware of multiple environment variables with the same effective name
CERT C++ Secure CodingENV02-CPPBeware of multiple environment variables with the same effective name
+ Content History
Submission DateSubmitterOrganizationSource
CLASPExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-10-29CWE Content TeamMITREInternal
updated Demonstrative_Examples, Description, Other_Notes
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 Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships

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Page Last Updated: May 05, 2017