CWE

Common Weakness Enumeration

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Home > CWE List > CWE-404: Improper Resource Shutdown or Release (4.18)
ID
CWE Glossary Definition

CWE-404: Improper Resource Shutdown or Release

Weakness ID: 404
Vulnerability Mapping: ALLOWED This CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review (with careful review of mapping notes)
Abstraction: 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.
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Description
The product does not release or incorrectly releases a resource before it is made available for re-use.
Extended Description
When a resource is created or allocated, the developer is responsible for properly releasing the resource as well as accounting for all potential paths of expiration or invalidation, such as a set period of time or revocation.
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.
Impact Details

DoS: Resource Consumption (Other); Varies by Context

Scope: Availability, Other

Most unreleased resource issues result in general software reliability problems, but if an attacker can intentionally trigger a resource leak, the attacker might be able to launch a denial of service attack by depleting the resource pool.

Read Application Data

Scope: Confidentiality

When a resource containing sensitive information is not correctly shutdown, it may expose the sensitive data in a subsequent allocation.
Potential Mitigations
Phase(s) Mitigation

Requirements

Strategy: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, languages such as Java, Ruby, and Lisp perform automatic garbage collection that releases memory for objects that have been deallocated.

Implementation
It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free memory in a function. If you allocate memory that you intend to free upon completion of the function, you must be sure to free the memory at all exit points for that function including error conditions.

Implementation
Memory should be allocated/freed using matching functions such as malloc/free, new/delete, and new[]/delete[].

Implementation
When releasing a complex object or structure, ensure that you properly dispose of all of its member components, not just the object itself.
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" (View-1000)
Nature Type ID Name
ChildOf Pillar Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things. 664 Improper Control of a Resource Through its Lifetime
ParentOf 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. 299 Improper Check for Certificate Revocation
ParentOf 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. 459 Incomplete Cleanup
ParentOf 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. 763 Release of Invalid Pointer or Reference
ParentOf 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. 772 Missing Release of Resource after Effective Lifetime
ParentOf 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. 1266 Improper Scrubbing of Sensitive Data from Decommissioned Device
PeerOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 239 Failure to Handle Incomplete Element
PeerOf 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. 405 Asymmetric Resource Consumption (Amplification)
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. 619 Dangling Database Cursor ('Cursor Injection')
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)
Nature Type ID Name
MemberOf View View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1003 Weaknesses for Simplified Mapping of Published Vulnerabilities
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 401 Missing Release of Memory after Effective Lifetime
ParentOf 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. 459 Incomplete Cleanup
ParentOf 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. 763 Release of Invalid Pointer or Reference
ParentOf 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. 772 Missing Release of Resource after Effective Lifetime
Relevant to the view "CISQ Quality Measures (2020)" (View-1305)
Nature Type ID Name
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 401 Missing Release of Memory after Effective Lifetime
ParentOf 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. 772 Missing Release of Resource after Effective Lifetime
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 775 Missing Release of File Descriptor or Handle after Effective Lifetime
Relevant to the view "CISQ Data Protection Measures" (View-1340)
Nature Type ID Name
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 761 Free of Pointer not at Start of Buffer
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 762 Mismatched Memory Management Routines
ParentOf 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. 763 Release of Invalid Pointer or Reference
ParentOf 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. 772 Missing Release of Resource after Effective Lifetime
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 775 Missing Release of File Descriptor or Handle after Effective Lifetime
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

Class: Not Language-Specific (Undetermined Prevalence)

Likelihood Of Exploit
Medium
Demonstrative Examples

Example 1


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.

(bad code)
Example Language: Java
private void processFile(string fName)
{
BufferReader fil = new BufferReader(new FileReader(fName));
String line;
while ((line = fil.ReadLine()) != null)
{
processLine(line);
}
}

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.

(good code)
Example Language: Java
private void processFile(string fName)
{
BufferReader fil = new BufferReader(new FileReader(fName));
String line;
while ((line = fil.ReadLine()) != null)
{
processLine(line);
}
fil.Close();
}


Example 2


This code attempts to open a connection to a database and catches any exceptions that may occur.

(bad code)
Example Language: Java
try {
Connection con = DriverManager.getConnection(some_connection_string);
}
catch ( Exception e ) {
log( e );
}

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.



Example 3


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.

(bad code)
Example Language: C#
...
SqlConnection conn = new SqlConnection(connString);
SqlCommand cmd = new SqlCommand(queryString);
cmd.Connection = conn;
conn.Open();
SqlDataReader rdr = cmd.ExecuteReader();
HarvestResults(rdr);
conn.Connection.Close();
...


Example 4


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.

(bad code)
Example Language: C
int decodeFile(char* fName) {
char buf[BUF_SZ];
FILE* f = fopen(fName, "r");
if (!f) {
printf("cannot open %s\n", fName);
return DECODE_FAIL;
}
else {
while (fgets(buf, BUF_SZ, f)) {
if (!checkChecksum(buf)) {
return DECODE_FAIL;
}
else {
decodeBlock(buf);
}
}
}
fclose(f);
return DECODE_SUCCESS;
}


Example 5


In this example, the program does not use matching functions such as malloc/free, new/delete, and new[]/delete[] to allocate/deallocate the resource.

(bad code)
Example Language: C++
class A {
void foo();
};
void A::foo(){
int *ptr;
ptr = (int*)malloc(sizeof(int));
delete ptr;
}


Example 6


In this example, the program calls the delete[] function on non-heap memory.

(bad code)
Example Language: C++
class A{
void foo(bool);
};
void A::foo(bool heap) {
int localArray[2] = {
11,22
};
int *p = localArray;
if (heap){
p = new int[2];
}
delete[] p;
}


Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference Description
Does not shut down named pipe connections if malformed data is sent.
Sockets not properly closed when attacker repeatedly connects and disconnects from server.
Chain: Return values of file/socket operations are not checked (CWE-252), allowing resultant consumption of file descriptors (CWE-772).
Weakness Ordinalities
Ordinality Description
Primary
(where the weakness exists independent of other weaknesses)
Improper release or shutdown of resources can be primary to resource exhaustion, performance, and information confidentiality problems to name a few.
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
Improper release or shutdown of resources can be resultant from improper error handling or insufficient resource tracking.
Detection Methods
Method Details

Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Resource clean up errors might be detected with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Effectiveness: Moderate

Manual Dynamic Analysis
Identify error conditions that are not likely to occur during normal usage and trigger them. For example, run the product under low memory conditions, run with insufficient privileges or permissions, interrupt a transaction before it is completed, or disable connectivity to basic network services such as DNS. Monitor the software for any unexpected behavior. If you trigger an unhandled exception or similar error that was discovered and handled by the application's environment, it may still indicate unexpected conditions that were not handled by the application itself.

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.)

Effectiveness: High
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. 398 7PK - Code Quality
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 730 OWASP Top Ten 2004 Category A9 - Denial of Service
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 743 CERT C Secure Coding Standard (2008) Chapter 10 - Input Output (FIO)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 752 2009 Top 25 - Risky Resource Management
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 857 The CERT Oracle Secure Coding Standard for Java (2011) Chapter 14 - Input Output (FIO)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 876 CERT C++ Secure Coding Section 08 - Memory Management (MEM)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 877 CERT C++ Secure Coding Section 09 - Input Output (FIO)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 882 CERT C++ Secure Coding Section 14 - Concurrency (CON)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 982 SFP Secondary Cluster: Failure to Release Resource
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1147 SEI CERT Oracle Secure Coding Standard for Java - Guidelines 13. Input Output (FIO)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1162 SEI CERT C Coding Standard - Guidelines 08. Memory Management (MEM)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1163 SEI CERT C Coding Standard - Guidelines 09. Input Output (FIO)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1306 CISQ Quality Measures - Reliability
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1308 CISQ Quality Measures - Security
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1309 CISQ Quality Measures - Efficiency
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1340 CISQ Data Protection Measures
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1416 Comprehensive Categorization: Resource Lifecycle Management
Vulnerability Mapping Notes
Usage ALLOWED-WITH-REVIEW
(this CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review)
Reason Abstraction

Rationale

This CWE entry is a Class and might have Base-level children that would be more appropriate

Comments

Examine children of this entry to see if there is a better fit
Notes

Relationship

Overlaps memory leaks, asymmetric resource consumption, malformed input errors.
Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
PLOVER Improper resource shutdown or release
7 Pernicious Kingdoms Unreleased Resource
OWASP Top Ten 2004 A9 CWE More Specific Denial of Service
CERT C Secure Coding FIO42-C CWE More Abstract Close files when they are no longer needed
CERT C Secure Coding MEM31-C CWE More Abstract Free dynamically allocated memory when no longer needed
The CERT Oracle Secure Coding Standard for Java (2011) FIO04-J Release resources when they are no longer needed
Software Fault Patterns SFP14 Failure to release resource
References
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 8: C++ Catastrophes." Page 143. McGraw-Hill. 2010.
Content History
Submissions
Submission Date Submitter Organization
2006年07月19日
(CWE Draft 3, 2006年07月19日) 		PLOVER
Modifications
Modification Date Modifier Organization
2023年10月26日 CWE Content Team MITRE
updated Observed_Examples
2023年06月29日 CWE Content Team MITRE
updated Mapping_Notes
2023年04月27日 CWE Content Team MITRE
updated Detection_Factors, Relationships, Time_of_Introduction
2023年01月31日 CWE Content Team MITRE
updated Description, Detection_Factors
2022年10月13日 CWE Content Team MITRE
updated Relationships
2021年07月20日 CWE Content Team MITRE
updated Related_Attack_Patterns
2021年03月15日 CWE Content Team MITRE
updated Demonstrative_Examples
2020年12月10日 CWE Content Team MITRE
updated Relationships
2020年08月20日 CWE Content Team MITRE
updated Relationships
2020年06月25日 CWE Content Team MITRE
updated Relationships
2020年02月24日 CWE Content Team MITRE
updated Relationships
2019年06月20日 CWE Content Team MITRE
updated Related_Attack_Patterns, Relationships
2019年01月03日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings, Type
2017年11月08日 CWE Content Team MITRE
updated Applicable_Platforms, Functional_Areas, Likelihood_of_Exploit, Relationships, Taxonomy_Mappings
2017年05月03日 CWE Content Team MITRE
updated Related_Attack_Patterns
2017年01月19日 CWE Content Team MITRE
updated Relationships
2015年12月07日 CWE Content Team MITRE
updated Relationships
2014年07月30日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2014年06月23日 CWE Content Team MITRE
updated Related_Attack_Patterns
2014年02月18日 CWE Content Team MITRE
updated Demonstrative_Examples
2012年05月11日 CWE Content Team MITRE
updated Demonstrative_Examples, References, Relationships, Taxonomy_Mappings
2011年09月13日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2011年06月27日 CWE Content Team MITRE
updated Common_Consequences
2011年06月01日 CWE Content Team MITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011年03月29日 CWE Content Team MITRE
updated Weakness_Ordinalities
2010年12月13日 CWE Content Team MITRE
updated Demonstrative_Examples
2010年06月21日 CWE Content Team MITRE
updated Detection_Factors, Potential_Mitigations
2010年02月16日 CWE Content Team MITRE
updated Potential_Mitigations, Relationships
2009年10月29日 CWE Content Team MITRE
updated Other_Notes
2009年07月27日 CWE Content Team MITRE
updated Demonstrative_Examples, Related_Attack_Patterns
2009年05月27日 CWE Content Team MITRE
updated Description, Relationships
2009年03月10日 CWE Content Team MITRE
updated Potential_Mitigations
2009年01月12日 CWE Content Team MITRE
updated Common_Consequences, Likelihood_of_Exploit, Other_Notes, Potential_Mitigations, Relationship_Notes, Relationships, Weakness_Ordinalities
2008年11月24日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2008年10月14日 CWE Content Team MITRE
updated Relationships
2008年09月08日 CWE Content Team MITRE
updated Description, Relationships, Other_Notes, Taxonomy_Mappings
2008年08月15日 Veracode
Suggested OWASP Top Ten 2004 mapping
2008年07月01日 Eric Dalci Cigital
updated Time_of_Introduction
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Page Last Updated: September 09, 2025

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