CWE-772: Missing Release of Resource after Effective Lifetime

Causes

• The following method never closes the new file handle. Given enough time, the Finalize() method for BufferReader should eventually call Close(), but there is no guarantee as to how long this action will take. In fact, there is no guarantee that Finalize() will ever be invoked. In a busy environment, the Operating System could use up all of the available file handles before the Close() function is called. The good code example simply adds an explicit call to the Close() function when the system is done using the file. Within a simple example such as this the problem is easy to see and fix. In a real system, the problem may be considerably more obscure.
• The following code attempts to open a new connection to a database, process the results returned by the database, and close the allocated SqlConnection object. The problem with the above code is that if an exception occurs while executing the SQL or processing the results, the SqlConnection object is not closed. If this happens often enough, the database will run out of available cursors and not be able to execute any more SQL queries.
• This code attempts to open a connection to a database and catches any exceptions that may occur. If an exception occurs after establishing the database connection and before the same connection closes, the pool of database connections may become exhausted. If the number of available connections is exceeded, other users cannot access this resource, effectively denying access to the application.
• Under normal conditions the following C# code executes a database query, processes the results returned by the database, and closes the allocated SqlConnection object. But if an exception occurs while executing the SQL or processing the results, the SqlConnection object is not closed. If this happens often enough, the database will run out of available cursors and not be able to execute any more SQL queries.
• The following C function does not close the file handle it opens if an error occurs. If the process is long-lived, the process can run out of file handles.

Remediation

• Requirements: [object Object]
• Implementation: It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free resources in a function. If you allocate resources that you intend to free upon completion of the function, you must be sure to free the resources at all exit points for that function including error conditions.
• Operation,Architecture and Design: [object Object]

Detection

• Automated Static Analysis: Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Related CWEs

• CWE-1091: Use of Object without Invoking Destructor Method
• CWE-401: Missing Release of Memory after Effective Lifetime
• CWE-404: Improper Resource Shutdown or Release
• CWE-404: Improper Resource Shutdown or Release
• CWE-404: Improper Resource Shutdown or Release
• CWE-404: Improper Resource Shutdown or Release
• CWE-775: Missing Release of File Descriptor or Handle after Effective Lifetime
• CWE-911: Improper Update of Reference Count

Related CVEs

Related CVE mappings appear after CVE records are cross-indexed.

ATT&CK Relevance

ATT&CK relevance is shown only when reviewed or responsibly inferred.