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

Définition

What is CWE-467?

This vulnerability occurs when a developer uses the sizeof() operator on a pointer variable instead of the data it points to, leading to incorrect size calculations and potential buffer overflows or underflows.

Using sizeof() on a pointer returns the size of the pointer itself (e.g., 4 or 8 bytes for the memory address), not the size of the allocated object or data structure it references. This is a common mistake when programmers intend to calculate buffer sizes, perform memory operations like memcpy, or allocate dynamic memory, resulting in calculations that are off by a factor of the pointer size. While sizeof(pointer) can be intentionally used for platform-specific code (like determining system word size), its presence usually indicates a logic bug. To avoid this, always ensure sizeof() is applied to the dereferenced pointer type (e.g., sizeof(*pointer)) or the actual data type name, especially when dealing with arrays, structs, or dynamically allocated memory blocks.

Impact réel

Real-world CVEs caused by CWE-467

Aucune référence CVE publique n'est liée à ce CWE dans le catalogue MITRE pour le moment.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

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.
2
In this example, sizeof(foo) returns the size of the pointer.
3
In this example, sizeof(*foo) returns the size of the data structure and not the size of the pointer.
4
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.
5
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).

Exemple de code vulnérable

Vulnerable C

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

Vulnérable C

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

Charge utile de l'attaquant

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

Charge utile de l'attaquant

pass5
  passABCDEFGH
  passWORD

Exemple de code sécurisé

Secure C

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

Sécurisé C

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

What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.

Liste de contrôle de prévention

How to prevent CWE-467

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.

Signaux de détection

How to detect CWE-467

Automated Static Analysis High

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.)

CWE-467

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Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-467 ?

This vulnerability occurs when a developer uses the sizeof() operator on a pointer variable instead of the data it points to, leading to incorrect size calculations and potential buffer overflows or underflows.

Quelle est la gravité de CWE-467 ?

MITRE évalue la probabilité d'exploitation comme Élevée — cette faiblesse est activement exploitée et doit être priorisée pour la remédiation.

Quels langages ou plateformes sont affectés par CWE-467 ?

MITRE lists the following affected platforms: C, C++.

Comment puis-je prévenir CWE-467 ?

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.

Comment Plexicus détecte et corrige CWE-467 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-467 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-467 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/467.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-467

CWE-131 Parent

Incorrect Calculation of Buffer Size

This vulnerability occurs when a program miscalculates the amount of memory needed for a buffer, potentially leading to a buffer overflow…

Ressources

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Use of sizeof() on a Pointer Type