The product contains an expression that will always evaluate to false.

Primary

Implementation

Other
Quality Degradation
Varies by Context

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.)
High

Testing
Use Static Analysis tools to spot such conditions.

In the following Java example the updateUserAccountOrder() method used within an e-business product ordering/inventory application will validate the product number that was ordered and the user account number. If they are valid, the method will update the product inventory, the user account, and the user order appropriately.

public void updateUserAccountOrder(String productNumber, String accountNumber) {
boolean isValidProduct = false;boolean isValidAccount = false;
if (validProductNumber(productNumber)) {isValidProduct = true;updateInventory(productNumber);}else {return;}
if (validAccountNumber(accountNumber)) {isValidProduct = true;updateAccount(accountNumber, productNumber);}
if (isValidProduct && isValidAccount) {updateAccountOrder(accountNumber, productNumber);}
}

However, the method never sets the isValidAccount variable after initializing it to false so the isValidProduct is mistakenly used twice. The result is that the expression "isValidProduct && isValidAccount" will always evaluate to false, so the updateAccountOrder() method will never be invoked. This will create serious problems with the product ordering application since the user account and inventory databases will be updated but the order will not be updated.
This can be easily corrected by updating the appropriate variable.

...if (validAccountNumber(accountNumber)) {isValidAccount = true;updateAccount(accountNumber, productNumber);}...

In the following example, the hasReadWriteAccess method uses bit masks and bit operators to determine if a user has read and write privileges for a particular process. The variable mask is defined as a bit mask from the BIT_READ and BIT_WRITE constants that have been defined. The variable mask is used within the predicate of the hasReadWriteAccess method to determine if the userMask input parameter has the read and write bits set.

#define BIT_READ 0x0001 // 00000001#define BIT_WRITE 0x0010 // 00010000
unsigned int mask = BIT_READ & BIT_WRITE; /* intended to use "|" */
// using "&", mask = 00000000// using "|", mask = 00010001
// determine if user has read and write accessint hasReadWriteAccess(unsigned int userMask) {
// if the userMask has read and write bits set// then return 1 (true)if (userMask & mask) {return 1;}
// otherwise return 0 (false)return 0;
}

However the bit operator used to initialize the mask variable is the AND operator rather than the intended OR operator (CWE-480), this resulted in the variable mask being set to 0. As a result, the if statement will always evaluate to false and never get executed.
The use of bit masks, bit operators and bitwise operations on variables can be difficult. If possible, try to use frameworks or libraries that provide appropriate functionality and abstract the implementation.

In the following example, the updateInventory method used within an e-business inventory application will update the inventory for a particular product. This method includes an if statement with an expression that will always evaluate to false. This is a common practice in C/C++ to introduce debugging statements quickly by simply changing the expression to evaluate to true and then removing those debugging statements by changing expression to evaluate to false. This is also a common practice for disabling features no longer needed.

int updateInventory(char* productNumber, int numberOfItems) {

int initCount = getProductCount(productNumber);
int updatedCount = initCount + numberOfItems;
int updated = updateProductCount(updatedCount);
// if statement for debugging purposes onlyif (1 == 0) {

char productName[128];productName = getProductName(productNumber);
printf("product %s initially has %d items in inventory \n", productName, initCount);printf("adding %d items to inventory for %s \n", numberOfItems, productName);
if (updated == 0) {printf("Inventory updated for product %s to %d items \n", productName, updatedCount);}
else {printf("Inventory not updated for product: %s \n", productName);}

}
return updated;
}

Using this practice for introducing debugging statements or disabling features creates dead code that can cause problems during code maintenance and potentially introduce vulnerabilities. To avoid using expressions that evaluate to false for debugging purposes a logging API or debugging API should be used for the output of debugging messages.

MSC00-C
Compile cleanly at high warning levels

SFP1
Glitch in computation

Allowed
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.
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.

CWE Community
2006-12-15
Draft 5
2006-12-15
Submitted by members of the CWE community to extend early CWE versions

Eric Dalci
Cigital
2008-07-01
updated Potential_Mitigations, Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Other_Notes

CWE Content Team
MITRE
2008-11-24
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2009-07-27
updated Demonstrative_Examples, Other_Notes, Potential_Mitigations

CWE Content Team
MITRE
2009-10-29
updated Demonstrative_Examples

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2011-06-27
updated Common_Consequences

CWE Content Team
MITRE
2011-09-13
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2012-05-11
updated Relationships

CWE Content Team
MITRE
2014-07-30
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2017-11-08
updated Applicable_Platforms, Demonstrative_Examples, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2020-02-24
updated Relationships, Type

CWE Content Team
MITRE
2020-08-20
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated Detection_Factors, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-04-03
4.17
2025-04-03
updated Demonstrative_Examples

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Weakness_Ordinalities