CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

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ID

CWE-585: Empty Synchronized Block

Weakness ID: 585
Abstraction: Variant
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software contains an empty synchronized block.
+ Extended Description
An empty synchronized block does not actually accomplish any synchronization and may indicate a troubled section of code. An empty synchronized block can occur because code no longer needed within the synchronized block is commented out without removing the synchronized block.
+ 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
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.710Improper Adherence to Coding Standards
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1006Bad Coding Practices
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.371State Issues
+ 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
+ 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

Java (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
Other

Technical Impact: Other

An empty synchronized block will wait until nobody else is using the synchronizer being specified. While this may be part of the desired behavior, because you haven't protected the subsequent code by placing it inside the synchronized block, nothing is stopping somebody else from modifying whatever it was you were waiting for while you run the subsequent code.
+ Demonstrative Examples

Example 1

The following code attempts to synchronize on an object, but does not execute anything in the synchronized block. This does not actually accomplish anything and may be a sign that a programmer is wrestling with synchronization but has not yet achieved the result they intend.

(bad code)
Example Language: Java 
synchronized(this) { }

Instead, in a correct usage, the synchronized statement should contain procedures that access or modify data that is exposed to multiple threads. For example, consider a scenario in which several threads are accessing student records at the same time. The method which sets the student ID to a new value will need to make sure that nobody else is accessing this data at the same time and will require synchronization.

(good code)
 
public void setID(int ID){
synchronized(this){
this.ID = ID;
}
}
+ Potential Mitigations

Phase: Implementation

When you come across an empty synchronized statement, or a synchronized statement in which the code has been commented out, try to determine what the original intentions were and whether or not the synchronized block is still necessary.
+ 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
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.987SFP Secondary Cluster: Multiple Locks/Unlocks
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
Software Fault PatternsSFP21Multiple locks/unlocks
+ References
[REF-478] "Intrinsic Locks and Synchronization (in Java)". <http://java.sun.com/docs/books/tutorial/essential/concurrency/locksync.html>.
+ Content History
Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes
2009-05-27CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Description, Other_Notes, Potential_Mitigations, References
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Relationships

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Page Last Updated: March 29, 2018