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Common Weakness Enumeration

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Home > CWE List > CWE-609: Double-Checked Locking (4.16)  
ID

CWE-609: Double-Checked Locking

Weakness ID: 609
Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: Base 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.
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+ Description
The product uses double-checked locking to access a resource without the overhead of explicit synchronization, but the locking is insufficient.
+ Extended Description
Double-checked locking refers to the situation where a programmer checks to see if a resource has been initialized, grabs a lock, checks again to see if the resource has been initialized, and then performs the initialization if it has not occurred yet. This should not be done, as it is not guaranteed to work in all languages and on all architectures. In summary, other threads may not be operating inside the synchronous block and are not guaranteed to see the operations execute in the same order as they would appear inside the synchronous block.
+ Common Consequences
Section HelpThis table 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
Integrity
Other

Technical Impact: Modify Application Data; Alter Execution Logic

+ Potential Mitigations

Phase: Implementation

While double-checked locking can be achieved in some languages, it is inherently flawed in Java before 1.5, and cannot be achieved without compromising platform independence. Before Java 1.5, only use of the synchronized keyword is known to work. Beginning in Java 1.5, use of the "volatile" keyword allows double-checked locking to work successfully, although there is some debate as to whether it achieves sufficient performance gains. See references.
+ Relationships
Section Help This table 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 Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 667 Improper Locking
CanPrecede Base 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. 367 Time-of-check Time-of-use (TOCTOU) Race Condition
Section Help This table 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 "Software Development" (CWE-699)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 411 Resource Locking Problems
+ Modes Of Introduction
Section HelpThe 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
Section HelpThis listing shows 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)

+ Demonstrative Examples

Example 1

It may seem that the following bit of code achieves thread safety while avoiding unnecessary synchronization...

(bad code)
Example Language: Java 
if (helper == null) {
synchronized (this) {
if (helper == null) {
helper = new Helper();
}
}
}
return helper;

The programmer wants to guarantee that only one Helper() object is ever allocated, but does not want to pay the cost of synchronization every time this code is called.

Suppose that helper is not initialized. Then, thread A sees that helper==null and enters the synchronized block and begins to execute:

(bad code)
 
helper = new Helper();

If a second thread, thread B, takes over in the middle of this call and helper has not finished running the constructor, then thread B may make calls on helper while its fields hold incorrect values.


+ Memberships
Section HelpThis 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 CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 853 The CERT Oracle Secure Coding Standard for Java (2011) Chapter 10 - Locking (LCK)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 986 SFP Secondary Cluster: Missing Lock
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1143 SEI CERT Oracle Secure Coding Standard for Java - Guidelines 09. Locking (LCK)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1401 Comprehensive Categorization: Concurrency
+ Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID may be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
+ Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
The CERT Oracle Secure Coding Standard for Java (2011) LCK10-J Do not use incorrect forms of the double-checked locking idiom
Software Fault Patterns SFP19 Missing Lock
+ References
[REF-490] David Bacon et al. "The "Double-Checked Locking is Broken" Declaration". <http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html>.
[REF-491] Jeremy Manson and Brian Goetz. "JSR 133 (Java Memory Model) FAQ". <http://www.cs.umd.edu/~pugh/java/memoryModel/jsr-133-faq.html#dcl>.
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 13, "Threading Vulnerabilities", Page 815. 1st Edition. Addison Wesley. 2006.
+ Content History
+ Submissions
Submission Date Submitter Organization
2007-05-07
(CWE Draft 6, 2007-05-07)
Anonymous Tool Vendor (under NDA)
+ Modifications
Modification Date Modifier Organization
2008-07-01 Eric Dalci Cigital
updated Context_Notes
2008-09-08 CWE Content Team MITRE
updated Description, Relationships, Taxonomy_Mappings
2008-11-24 CWE Content Team MITRE
updated Demonstrative_Examples
2009-01-12 CWE Content Team MITRE
updated Relationships
2009-05-27 CWE Content Team MITRE
updated Relationships
2009-10-29 CWE Content Team MITRE
updated Taxonomy_Mappings
2010-12-13 CWE Content Team MITRE
updated Relationships
2011-06-01 CWE Content Team MITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11 CWE Content Team MITRE
updated Demonstrative_Examples, References, Relationships
2012-10-30 CWE Content Team MITRE
updated Potential_Mitigations
2014-07-30 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2019-01-03 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2020-02-24 CWE Content Team MITRE
updated Relationships
2023-01-31 CWE Content Team MITRE
updated Description
2023-04-27 CWE Content Team MITRE
updated Relationships
2023-06-29 CWE Content Team MITRE
updated Mapping_Notes
+ Previous Entry Names
Change Date Previous Entry Name
2008-04-11 Double Checked Locking
Page Last Updated: November 19, 2024