| CWE-609: Double-Checked Locking
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     Edit Custom FilterThe product uses double-checked locking to access a resource without the overhead of explicit synchronization, but the locking is insufficient. 
                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.
              This 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. 
 
  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" (View-1000) 
  Relevant to the view "Software Development" (View-699) 
  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. 
  This 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. 
 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) 
                                    
                                    Example Language: Java 
                                    
                                 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.  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. 
 
 
 
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