CWE

Common Weakness Enumeration

A community-developed list of SW & HW weaknesses that can become vulnerabilities

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ID

CWE-413: Improper Resource Locking

Weakness ID: 413
Vulnerability Mapping: ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities
Abstraction: BaseBase - 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 does not lock or does not correctly lock a resource when the product must have exclusive access to the resource.
+ Extended Description
When a resource is not properly locked, an attacker could modify the resource while it is being operated on by the product. This might violate the product's assumption that the resource will not change, potentially leading to unexpected behaviors.
+ 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.
ScopeImpactLikelihood
Integrity
Availability

Technical Impact: Modify Application Data; DoS: Instability; DoS: Crash, Exit, or Restart

+ Potential Mitigations

Phase: Architecture and Design

Use a non-conflicting privilege scheme.

Phases: Architecture and Design; Implementation

Use synchronization when locking a resource.
+ Relationships
Section HelpThis 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)
NatureTypeIDName
ChildOfClassClass - 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.667Improper Locking
ParentOfVariantVariant - 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.591Sensitive Data Storage in Improperly Locked Memory
Section HelpThis 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)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.411Resource 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.
PhaseNote
Architecture and Design
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)

+ Demonstrative Examples

Example 1

The following function attempts to acquire a lock in order to perform operations on a shared resource.

(bad code)
Example Language:
void f(pthread_mutex_t *mutex) {
pthread_mutex_lock(mutex);

/* access shared resource */


pthread_mutex_unlock(mutex);
}

However, the code does not check the value returned by pthread_mutex_lock() for errors. If pthread_mutex_lock() cannot acquire the mutex for any reason, the function may introduce a race condition into the program and result in undefined behavior.

In order to avoid data races, correctly written programs must check the result of thread synchronization functions and appropriately handle all errors, either by attempting to recover from them or reporting them to higher levels.

(good code)
Example Language:
int f(pthread_mutex_t *mutex) {
int result;

result = pthread_mutex_lock(mutex);
if (0 != result)
return result;


/* access shared resource */


return pthread_mutex_unlock(mutex);
}

Example 2

This Java example shows a simple BankAccount class with deposit and withdraw methods.

(bad code)
Example Language: Java 
public class BankAccount {

// variable for bank account balance
private double accountBalance;

// constructor for BankAccount
public BankAccount() {
accountBalance = 0;
}

// method to deposit amount into BankAccount
public void deposit(double depositAmount) {

double newBalance = accountBalance + depositAmount;
accountBalance = newBalance;
}

// method to withdraw amount from BankAccount
public void withdraw(double withdrawAmount) {

double newBalance = accountBalance - withdrawAmount;
accountBalance = newBalance;
}

// other methods for accessing the BankAccount object
...
}

However, the deposit and withdraw methods have shared access to the account balance private class variable. This can result in a race condition if multiple threads attempt to call the deposit and withdraw methods simultaneously where the account balance is modified by one thread before another thread has completed modifying the account balance. For example, if a thread attempts to withdraw funds using the withdraw method before another thread that is depositing funds using the deposit method completes the deposit then there may not be sufficient funds for the withdraw transaction.

To prevent multiple threads from having simultaneous access to the account balance variable the deposit and withdraw methods should be synchronized using the synchronized modifier.

(good code)
Example Language: Java 
public class BankAccount {
...
// synchronized method to deposit amount into BankAccount
public synchronized void deposit(double depositAmount) {
...
}

// synchronized method to withdraw amount from BankAccount
public synchronized void withdraw(double withdrawAmount) {
...
}

...
}

An alternative solution is to use a lock object to ensure exclusive access to the bank account balance variable. As shown below, the deposit and withdraw methods use the lock object to set a lock to block access to the BankAccount object from other threads until the method has completed updating the bank account balance variable.

(good code)
Example Language: Java 
public class BankAccount {
...
// lock object for thread access to methods
private ReentrantLock balanceChangeLock;

// condition object to temporarily release lock to other threads
private Condition sufficientFundsCondition;

// method to deposit amount into BankAccount
public void deposit(double amount) {

// set lock to block access to BankAccount from other threads
balanceChangeLock.lock();
try {
double newBalance = balance + amount;
balance = newBalance;

// inform other threads that funds are available
sufficientFundsCondition.signalAll();
} catch (Exception e) {...}
finally {
// unlock lock object
balanceChangeLock.unlock();
}
}

// method to withdraw amount from bank account
public void withdraw(double amount) {

// set lock to block access to BankAccount from other threads
balanceChangeLock.lock();
try {
while (balance < amount) {

// temporarily unblock access

// until sufficient funds are available
sufficientFundsCondition.await();
}
double newBalance = balance - amount;
balance = newBalance;
} catch (Exception e) {...}
finally {
// unlock lock object
balanceChangeLock.unlock();
}
}
...
}

+ Observed Examples
ReferenceDescription
Chain: an operating system kernel has insufficent resource locking (CWE-413) leading to a use after free (CWE-416).
+ Detection Methods

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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.852The CERT Oracle Secure Coding Standard for Java (2011) Chapter 9 - Visibility and Atomicity (VNA)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.853The CERT Oracle Secure Coding Standard for Java (2011) Chapter 10 - Locking (LCK)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.986SFP Secondary Cluster: Missing Lock
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1142SEI CERT Oracle Secure Coding Standard for Java - Guidelines 08. Visibility and Atomicity (VNA)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1401Comprehensive Categorization: Concurrency
+ Vulnerability Mapping Notes

Usage: ALLOWED

(this CWE ID could 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 NameNode IDFitMapped Node Name
PLOVERInsufficient Resource Locking
The CERT Oracle Secure Coding Standard for Java (2011)VNA00-JEnsure visibility when accessing shared primitive variables
The CERT Oracle Secure Coding Standard for Java (2011)VNA02-JEnsure that compound operations on shared variables are atomic
The CERT Oracle Secure Coding Standard for Java (2011)LCK00-JUse private final lock objects to synchronize classes that may interact with untrusted code
Software Fault PatternsSFP19Missing Lock
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19
(CWE Draft 3, 2006-07-19)
PLOVER
+ Contributions
Contribution DateContributorOrganization
2010-04-30Martin SeborCisco Systems, Inc.
Provided Demonstrative Example
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2010-06-21CWE Content TeamMITRE
updated Demonstrative_Examples
2010-09-27CWE Content TeamMITRE
updated Description, Name
2010-12-13CWE Content TeamMITRE
updated Demonstrative_Examples
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms
2019-01-03CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2020-02-24CWE Content TeamMITRE
updated Relationships
2021-03-15CWE Content TeamMITRE
updated Demonstrative_Examples
2023-01-31CWE Content TeamMITRE
updated Description
2023-04-27CWE Content TeamMITRE
updated Detection_Factors, Relationships
2023-06-29CWE Content TeamMITRE
updated Mapping_Notes
2023-10-26CWE Content TeamMITRE
updated Observed_Examples
+ Previous Entry Names
Change DatePrevious Entry Name
2010-09-27Insufficient Resource Locking
Page Last Updated: July 16, 2024