Base weakness

Draft

CWE-772: Missing Release of Resource after Effective Lifetime

The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.

Recorded CVEs

With this primary weakness

KEVs

In the CISA KEV catalog

High

Likelihood of exploit

Per MITRE

Base

Abstraction

MITRE classification

Overview

CWE-772 (Missing Release of Resource after Effective Lifetime) is a base-level software weakness catalogued by MITRE in the Common Weakness Enumeration (CWE). It describes a recurring type of mistake that can lead to exploitable security vulnerabilities.

Real-world CVEs

Code examples

Illustrative examples from MITRE showing how the weakness appears in code.

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.

Vulnerable example

java

private void processFile(string fName)

Safe example

java

private void processFile(string fName)

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.

Vulnerable example

csharp

SqlConnection conn = new SqlConnection(connString);

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.

Vulnerable example

java

try {

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.

Vulnerable example

int decodeFile(char* fName) {

CWE-772: Missing Release of Resource after Effective Lifetime

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Automated Static Analysis

Code examples

Illustrative examples

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

What is CWE-772?

What CVEs are caused by CWE-772?

How do you prevent CWE-772?

How is CWE-772 detected?

What are the consequences of CWE-772?

Is CWE-772 actively exploited?

References

Stay ahead of CWE-772

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to prevent it

How to detect it

Automated Static Analysis

Code examples

Illustrative examples

Related weaknesses

Parent

Child

Related

Terminology & mappings

Mapped taxonomies

Attack patterns

Frequently asked questions

What is CWE-772?

What CVEs are caused by CWE-772?

How do you prevent CWE-772?

How is CWE-772 detected?

What are the consequences of CWE-772?

Is CWE-772 actively exploited?

References

Stay ahead of CWE-772