The product does not correctly convert an object, resource, or structure from one type to a different type.

Primary

Implementation

Other
Other

Fuzzing
Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
High

In this example, depending on the return value of accecssmainframe(), the variable amount can hold a negative value when it is returned. Because the function is declared to return an unsigned value, amount will be implicitly cast to an unsigned number.

unsigned int readdata () {int amount = 0;...amount = accessmainframe();...return amount;}

If the return value of accessmainframe() is -1, then the return value of readdata() will be 4,294,967,295 on a system that uses 32-bit integers.

The following code uses a union to support the representation of different types of messages. It formats messages differently, depending on their type.

#define NAME_TYPE 1#define ID_TYPE 2
struct MessageBuffer{int msgType;union {char *name;int nameID;};};

int main (int argc, char **argv) {
struct MessageBuffer buf;char *defaultMessage = "Hello World";
buf.msgType = NAME_TYPE;buf.name = defaultMessage;printf("Pointer of buf.name is %p\n", buf.name);
/* This particular value for nameID is used to make the code architecture-independent. If coming from untrusted input, it could be any value. */

buf.nameID = (int)(defaultMessage + 1);printf("Pointer of buf.name is now %p\n", buf.name);if (buf.msgType == NAME_TYPE) {printf("Message: %s\n", buf.name);}else {printf("Message: Use ID %d\n", buf.nameID);}
}

The code intends to process the message as a NAME_TYPE, and sets the default message to "Hello World." However, since both buf.name and buf.nameID are part of the same union, they can act as aliases for the same memory location, depending on memory layout after compilation.
As a result, modification of buf.nameID - an int - can effectively modify the pointer that is stored in buf.name - a string.
Execution of the program might generate output such as:

Pointer of name is 10830
Pointer of name is now 10831
Message: ello World

Notice how the pointer for buf.name was changed, even though buf.name was not explicitly modified.
In this case, the first "H" character of the message is omitted. However, if an attacker is able to fully control the value of buf.nameID, then buf.name could contain an arbitrary pointer, leading to out-of-bounds reads or writes.

CVE-2021-43537
Chain: in a web browser, an unsigned 64-bit integer is forcibly cast to a 32-bit integer (CWE-681) and potentially leading to an integer overflow (CWE-190). If an integer overflow occurs, this can cause heap memory corruption (CWE-122)
https://www.cve.org/CVERecord?id=CVE-2021-43537

CVE-2022-3979
Chain: data visualization program written in PHP uses the "!=" operator instead of the type-strict "!==" operator (CWE-480) when validating hash values, potentially leading to an incorrect type conversion (CWE-704)
https://www.cve.org/CVERecord?id=CVE-2022-3979

EXP05-C
Do not cast away a const qualification

EXP39-C
Do not access a variable through a pointer of an incompatible type
CWE More Abstract

INT31-C
Ensure that integer conversions do not result in lost or misinterpreted data
CWE More Abstract

INT36-C
Converting a pointer to integer or integer to pointer
CWE More Abstract

STR34-C
Cast characters to unsigned types before converting to larger integer sizes
CWE More Abstract

STR37-C
Arguments to character handling functions must be representable as an unsigned char
CWE More Abstract

SFP1
Glitch in computation

ASCRM-CWE-704

Allowed-with-Review
This CWE entry is a Class and might have Base-level children that would be more appropriate
Examine children of this entry to see if there is a better fit

CWE Content Team
MITRE
2008-09-09
1.0
2008-09-09
Note: this date reflects when the entry was first published. Draft versions of this entry were provided to members of the CWE community and modified between Draft 9 and 1.0.

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

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

CWE Content Team
MITRE
2009-05-27
updated Description

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences, Relationships

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
2015-12-07
updated Relationships

CWE Content Team
MITRE
2017-01-19
updated Relationships

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

CWE Content Team
MITRE
2019-01-03
updated References, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2019-06-20
updated Relationships

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2020-08-20
updated Relationships

CWE Content Team
MITRE
2020-12-10
updated Relationships

CWE Content Team
MITRE
2022-10-13
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

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

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2023-10-26
updated Demonstrative_Examples, Observed_Examples

CWE Content Team
MITRE
2024-02-29
4.14
2024-02-29
updated Observed_Examples

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