CWE - CWE-585: Empty Synchronized Block (4.4)

Weakness ID: 585

Abstraction: Base
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)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.	1071	Empty Code Block

Relevant to the view "Software Development" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	557	Concurrency 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 life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Phase	Note
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.

Scope	Impact	Likelihood
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.

Weakness Ordinalities

Ordinality	Description
Indirect	(where the weakness is a quality issue that might indirectly make it easier to introduce security-relevant weaknesses or make them more difficult to detect)

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.

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	987	SFP Secondary Cluster: Multiple Locks/Unlocks

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
Software Fault Patterns	SFP21		Multiple locks/unlocks

References

[REF-478] "Intrinsic Locks and Synchronization (in Java)". <http://java.sun.com/docs/books/tutorial/essential/concurrency/locksync.html>.

Content History

Submissions
Submission Date	Submitter	Organization
2006-12-15	CWE Community
2006-12-15	Submitted by members of the CWE community to extend early CWE versions
Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Potential_Mitigations, Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Relationships, Other_Notes
2009-05-27	CWE Content Team	MITRE
2009-05-27	updated Common_Consequences, Demonstrative_Examples, Description, Other_Notes, Potential_Mitigations, References
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships, Taxonomy_Mappings
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Relationships
2019-01-03	CWE Content Team	MITRE
2019-01-03	updated Relationships, Weakness_Ordinalities
2020-02-24	CWE Content Team	MITRE
2020-02-24	updated Relationships, Type


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Common Weakness Enumeration

CWE-585: Empty Synchronized Block