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.
CWE-469 Base Brouillon
Use of Pointer Subtraction to Determine Size
This vulnerability occurs when a program calculates a size or offset by subtracting two memory pointers, but the pointers point to locations in different memory blocks, leading to an incorrect and…
Définition
What is CWE-469?
This vulnerability occurs when a program calculates a size or offset by subtracting two memory pointers, but the pointers point to locations in different memory blocks, leading to an incorrect and potentially dangerous result.
Pointer subtraction is a valid C/C++ operation, but it only yields a meaningful size or element count when both pointers point within the same contiguous memory allocation (like a single array or buffer). When developers use this trick on pointers from different allocations, the calculation produces a nonsensical value based on the arbitrary memory distance between the two chunks. This flawed size is then often used in buffer operations, leading to out-of-bounds reads or writes, memory corruption, and crashes.
Detecting these flaws manually is tricky because the code looks mathematically simple. While SAST tools can flag the pattern, Plexicus uses AI to analyze the pointer origins and suggest the correct fix—such as storing the allocation size separately—saving hours of debugging. Managing this at scale across a large codebase is difficult; an ASPM like Plexicus can help you track and remediate these subtle memory flaws across your entire application stack.
Impact réel
Real-world CVEs caused by CWE-469
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
Identifier un chemin de code qui traite des entrées non fiables sans validation.
- 2
Élaborer une charge utile qui exploite le comportement non sécurisé — injection, traversal, débordement ou abus de logique.
- 3
Délivrer la charge utile via une requête normale et observer la réaction de l'application.
- 4
Itérer jusqu'à ce que la réponse divulgue des données, exécute le code de l'attaquant ou élève les privilèges.
Exemple de code vulnérable
Vulnerable C
The following example contains the method size that is used to determine the number of nodes in a linked list. The method is passed a pointer to the head of the linked list.
struct node {
int data;
struct node* next;
};
```
// Returns the number of nodes in a linked list from*
*// the given pointer to the head of the list.*
int size(struct node* head) {
```
struct node* current = head;
struct node* tail;
while (current != NULL) {
tail = current;
current = current->next;
}
return tail - head;
}
```
// other methods for manipulating the list*
... Exemple de code sécurisé
Secure C
However, the method creates a pointer that points to the end of the list and uses pointer subtraction to determine the number of nodes in the list by subtracting the tail pointer from the head pointer. There no guarantee that the pointers exist in the same memory area, therefore using pointer subtraction in this way could return incorrect results and allow other unintended behavior. In this example a counter should be used to determine the number of nodes in the list, as shown in the following code.
...
int size(struct node* head) {
struct node* current = head;
int count = 0;
while (current != NULL) {
count++;
current = current->next;
}
return count;
} 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-469
- Implementation Save an index variable. This is the recommended solution. Rather than subtract pointers from one another, use an index variable of the same size as the pointers in question. Use this variable to "walk" from one pointer to the other and calculate the difference. Always validate this number.
Signaux de détection
How to detect CWE-469
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.)
Plexicus détecte automatiquement CWE-469 et ouvre une PR de correction en moins de 60 secondes.
Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.
Questions fréquentes Qu'est-ce que CWE-469 ?
Quelle est la gravité de CWE-469 ?
Quels langages ou plateformes sont affectés par CWE-469 ?
Comment puis-je prévenir CWE-469 ?
Comment Plexicus détecte et corrige CWE-469 ?
Où puis-je en savoir plus sur CWE-469 ?
Frequently asked questions
Qu'est-ce que CWE-469 ?
This vulnerability occurs when a program calculates a size or offset by subtracting two memory pointers, but the pointers point to locations in different memory blocks, leading to an incorrect and potentially dangerous result.
Quelle est la gravité de CWE-469 ?
MITRE évalue la probabilité d'exploitation comme Moyenne — l'exploitation est réaliste mais nécessite généralement des conditions spécifiques.
Quels langages ou plateformes sont affectés par CWE-469 ?
MITRE lists the following affected platforms: C, C++.
Comment puis-je prévenir CWE-469 ?
Save an index variable. This is the recommended solution. Rather than subtract pointers from one another, use an index variable of the same size as the pointers in question. Use this variable to "walk" from one pointer to the other and calculate the difference. Always validate this number.
Comment Plexicus détecte et corrige CWE-469 ?
Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-469 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-469 ?
MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/469.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.
Faiblesses associées
Weaknesses related to CWE-469
CWE-682 Parent
Incorrect Calculation
This vulnerability occurs when software performs a calculation that produces wrong or unexpected results, which are then used to make…
CWE-128 Frère
Wrap-around Error
A wrap-around error happens when a variable exceeds the maximum value its data type can hold, causing it to unexpectedly reset to a very…
CWE-131 Frère
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…
CWE-1335 Frère
Incorrect Bitwise Shift of Integer
This vulnerability occurs when a program attempts to shift an integer's bits by an invalid amount—either a negative number or a value…
CWE-1339 Frère
Insufficient Precision or Accuracy of a Real Number
This vulnerability occurs when a program uses a data type or algorithm that cannot accurately represent or calculate the fractional part…
CWE-135 Frère
Incorrect Calculation of Multi-Byte String Length
This vulnerability occurs when software incorrectly measures the length of strings containing multi-byte or wide characters, leading to…
CWE-190 Frère
Integer Overflow or Wraparound
Integer overflow or wraparound occurs when a calculation produces a numeric result that exceeds the maximum value a variable can hold.…
CWE-191 Frère
Integer Underflow (Wrap or Wraparound)
Integer underflow occurs when a subtraction operation results in a value smaller than the data type's minimum limit, causing the value to…
CWE-193 Frère
Off-by-one Error
An off-by-one error occurs when a program incorrectly calculates a boundary, such as a loop counter or array index, by being one unit too…
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