Common Weakness Enumeration

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CWE-543: Use of Singleton Pattern Without Synchronization in a Multithreaded Context

Weakness ID: 543
Abstraction: Variant
Structure: Simple
Status: Incomplete
Presentation Filter:
+ Description
The software uses the singleton pattern when creating a resource within a multithreaded environment.
+ Extended Description
The use of a singleton pattern may not be thread-safe.
+ 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)
ChildOfBaseBase820Missing Synchronization
+ Relevant to the view "Development Concepts" (CWE-699)
MemberOfCategoryCategory381J2EE Time and State Issues
ChildOfBaseBase820Missing Synchronization
+ 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.

+ 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.


Java (Undetermined Prevalence)

C++ (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.


Technical Impact: Other; Modify Application Data

+ Demonstrative Examples

Example 1

This method is part of a singleton pattern, yet the following singleton() pattern is not thread-safe. It is possible that the method will create two objects instead of only one.

(bad code)
Example Language: Java 
private static NumberConverter singleton;
public static NumberConverter get_singleton() {
if (singleton == null) {
singleton = new NumberConverter();

return singleton;


Consider the following course of events:

  • Thread A enters the method, finds singleton to be null, begins the NumberConverter constructor, and then is swapped out of execution.
  • Thread B enters the method and finds that singleton remains null. This will happen if A was swapped out during the middle of the constructor, because the object reference is not set to point at the new object on the heap until the object is fully initialized.
  • Thread B continues and constructs another NumberConverter object and returns it while exiting the method.
  • Thread A continues, finishes constructing its NumberConverter object, and returns its version.

At this point, the threads have created and returned two different objects.

+ Potential Mitigations

Phase: Architecture and Design

Use the Thread-Specific Storage Pattern. See References.

Phase: Implementation

Do not use member fields to store information in the Servlet. In multithreading environments, storing user data in Servlet member fields introduces a data access race condition.

Phase: Implementation

Avoid using the double-checked locking pattern in language versions that cannot guarantee thread safety. This pattern may be used to avoid the overhead of a synchronized call, but in certain versions of Java (for example), this has been shown to be unsafe because it still introduces a race condition (CWE-209).

Effectiveness: Limited

+ 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 Java Secure CodingMSC07-JPrevent multiple instantiations of singleton objects
Software Fault PatternsSFP19Missing Lock
+ References
[REF-474] Douglas C. Schmidt, Timothy H. Harrison and Nat Pryce. "Thread-Specifc Storage for C/C++". <>.
+ Content History
Submission DateSubmitterOrganization
Anonymous Tool Vendor (under NDA)
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2010-09-27CWE Content TeamMITRE
updated Name
2010-12-13CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples, Description, Potential_Mitigations, References, Relationships, Taxonomy_Mappings
2011-03-29CWE Content TeamMITRE
updated Demonstrative_Examples
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2010-09-27Use of Singleton Pattern in a Non-thread-safe Manner

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Page Last Updated: January 18, 2018