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CWE-467: Use of sizeof() on a Pointer Type

Weakness ID: 467
Abstraction: Variant
Structure: Simple
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+ Description
The code calls sizeof() on a malloced pointer type, which always returns the wordsize/8. This can produce an unexpected result if the programmer intended to determine how much memory has been allocated.
+ Extended Description
The use of sizeof() on a pointer can sometimes generate useful information. An obvious case is to find out the wordsize on a platform. More often than not, the appearance of sizeof(pointer) indicates a bug.
+ 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)
ChildOfBaseBase - 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.131Incorrect Calculation of Buffer Size
+ 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.
+ 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.


C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

+ 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.

Technical Impact: Modify Memory; Read Memory

This error can often cause one to allocate a buffer that is much smaller than what is needed, leading to resultant weaknesses such as buffer overflows.
+ Likelihood Of Exploit
+ Demonstrative Examples

Example 1

Care should be taken to ensure sizeof returns the size of the data structure itself, and not the size of the pointer to the data structure.

In this example, sizeof(foo) returns the size of the pointer.

(bad code)
Example Language:
double *foo;
foo = (double *)malloc(sizeof(foo));

In this example, sizeof(*foo) returns the size of the data structure and not the size of the pointer.

(good code)
Example Language:
double *foo;
foo = (double *)malloc(sizeof(*foo));

Example 2

This example defines a fixed username and password. The AuthenticateUser() function is intended to accept a username and a password from an untrusted user, and check to ensure that it matches the username and password. If the username and password match, AuthenticateUser() is intended to indicate that authentication succeeded.

(bad code)

/* Ignore CWE-259 (hard-coded password) and CWE-309 (use of password system for authentication) for this example. */

char *username = "admin";
char *pass = "password";

int AuthenticateUser(char *inUser, char *inPass) {
printf("Sizeof username = %d\n", sizeof(username));
printf("Sizeof pass = %d\n", sizeof(pass));

if (strncmp(username, inUser, sizeof(username))) {
printf("Auth failure of username using sizeof\n");
/* Because of CWE-467, the sizeof returns 4 on many platforms and architectures. */

if (! strncmp(pass, inPass, sizeof(pass))) {
printf("Auth success of password using sizeof\n");
else {
printf("Auth fail of password using sizeof\n");

int main (int argc, char **argv)
int authResult;

if (argc < 3) {
ExitError("Usage: Provide a username and password");
authResult = AuthenticateUser(argv[1], argv[2]);
if (authResult != AUTH_SUCCESS) {
ExitError("Authentication failed");
else {

In AuthenticateUser(), because sizeof() is applied to a parameter with an array type, the sizeof() call might return 4 on many modern architectures. As a result, the strncmp() call only checks the first four characters of the input password, resulting in a partial comparison (CWE-187), leading to improper authentication (CWE-287).

Because of the partial comparison, any of these passwords would still cause authentication to succeed for the "admin" user:

(attack code)

Because only 4 characters are checked, this significantly reduces the search space for an attacker, making brute force attacks more feasible.

The same problem also applies to the username, so values such as "adminXYZ" and "administrator" will succeed for the username.

+ Potential Mitigations

Phase: Implementation

Use expressions such as "sizeof(*pointer)" instead of "sizeof(pointer)", unless you intend to run sizeof() on a pointer type to gain some platform independence or if you are allocating a variable on the stack.
+ Weakness Ordinalities
(where the weakness exists independent of other weaknesses)
+ 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.
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.737CERT C Secure Coding Standard (2008) Chapter 4 - Expressions (EXP)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.740CERT C Secure Coding Standard (2008) Chapter 7 - Arrays (ARR)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.874CERT C++ Secure Coding Section 06 - Arrays and the STL (ARR)
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.974SFP Secondary Cluster: Incorrect Buffer Length Computation
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1162SEI CERT C Coding Standard - Guidelines 08. Memory Management (MEM)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1408Comprehensive Categorization: Incorrect Calculation
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPUse of sizeof() on a pointer type
CERT C Secure CodingARR01-CDo not apply the sizeof operator to a pointer when taking the size of an array
CERT C Secure CodingMEM35-CCWE More AbstractAllocate sufficient memory for an object
Software Fault PatternsSFP10Incorrect Buffer Length Computation
+ References
[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <>.
[REF-442] Robert Seacord. "EXP01-A. Do not take the sizeof a pointer to determine the size of a type". <>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-08-01KDM Analytics
added/updated white box definitions
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-03-10CWE Content TeamMITRE
updated Demonstrative_Examples
2009-12-28CWE Content TeamMITRE
updated Demonstrative_Examples
2010-02-16CWE Content TeamMITRE
updated Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-06-27CWE Content TeamMITRE
updated Common_Consequences
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Relationships
2014-06-23CWE Content TeamMITRE
updated Description, Other_Notes
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Demonstrative_Examples, Taxonomy_Mappings, White_Box_Definitions
2019-01-03CWE Content TeamMITRE
updated Relationships
2020-02-24CWE Content TeamMITRE
updated References
2023-04-27CWE Content TeamMITRE
updated Detection_Factors, Relationships
Page Last Updated: April 27, 2023