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

Code Examples & CVEs

Demonstrative Examples

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.

BadC

double *foo;...foo = (double *)malloc(sizeof(foo));

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.

GoodC

double *foo;...foo = (double *)malloc(sizeof(*foo));

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.

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).

BadC

/* 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");return(AUTH_FAIL);}                            /* 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");return(AUTH_SUCCESS);}else {printf("Auth fail of password using sizeof\n");return(AUTH_FAIL);}                      }                      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 {DoAuthenticatedTask(argv[1]);}                      }

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-467 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-467, Use of sizeof() on a Pointer Type, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Use of sizeof() on a Pointer Type during Implementation

MITRE associates mitigation with Implementation; documented detection approaches include Automated Static Analysis; recorded impacts include Modify Memory, and Read Memory. Use these source-defined anchors to turn CWE-467 into implementation, review, and verification checks for the affected component.

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

Triage CWE-467 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-467, Use of sizeof() on a Pointer Type, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-467

Apply MITRE's full root-cause mapping guidance when using CWE-467, Use of sizeof() on a Pointer Type. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-467 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-467, Use of sizeof() on a Pointer Type. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-467: Use of sizeof() on a Pointer Type?+

CWE-467: Use of sizeof() on a Pointer Type is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The code calls sizeof() on a pointer type, which can be an incorrect calculation if the programmer intended to determine the size of the data that is being pointed to. 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.

What are the security consequences of Use of sizeof() on a Pointer Type?+

If exploited, CWE-467 (Use of sizeof() on a Pointer Type) it can compromise Integrity and Confidentiality, leading to outcomes such as Modify Memory and Read Memory.

How do you prevent or mitigate Use of sizeof() on a Pointer Type?+

Recommended mitigations for CWE-467 include: 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.

Which programming languages are affected by Use of sizeof() on a Pointer Type?+

CWE-467 commonly affects C and C++. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-467 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

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

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