CWE-704: Incorrect Type Conversion or Cast
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Edit Custom FilterThe product does not correctly convert an object, resource, or structure from one type to a different type.
This 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.
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" (CWE-1000)
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
The 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.
This 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 C (Often Prevalent) C++ (Often Prevalent) Class: Not Language-Specific (Undetermined Prevalence) Example 1 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. (bad code)
Example Language: C
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. Example 2 The following code uses a union to support the representation of different types of messages. It formats messages differently, depending on their type. (bad code)
Example Language: C
#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.
This 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.
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