CWE-469: Use of Pointer Subtraction to Determine Size

Code Examples & CVEs

Demonstrative Examples

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.

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.

BadC

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                      ...

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.

GoodC

...                      int size(struct node* head) {struct node* current = head;int count = 0;while (current != NULL) {count++;current = current->next;}return count;}

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-469 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-469, Use of Pointer Subtraction to Determine Size, 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 Pointer Subtraction to Determine Size during Implementation

MITRE associates mitigation with Implementation; documented detection approaches include Fuzzing, and Automated Static Analysis; recorded impacts include Modify Memory, Read Memory, Execute Unauthorized Code or Commands, and Gain Privileges or Assume Identity. Use these source-defined anchors to turn CWE-469 into implementation, review, and verification checks for the affected component.

CWE-469: Use of Pointer Subtraction to Determine Size — MITRE CWE

Triage CWE-469 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-469, Use of Pointer Subtraction to Determine Size, 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-469

Apply MITRE's full root-cause mapping guidance when using CWE-469, Use of Pointer Subtraction to Determine Size. 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-469 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-469, Use of Pointer Subtraction to Determine Size. 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-469: Use of Pointer Subtraction to Determine Size?+

CWE-469: Use of Pointer Subtraction to Determine Size is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product subtracts one pointer from another in order to determine size, but this calculation can be incorrect if the pointers do not exist in the same memory chunk.

What are the security consequences of Use of Pointer Subtraction to Determine Size?+

If exploited, CWE-469 (Use of Pointer Subtraction to Determine Size) it can compromise Access Control, Integrity, Confidentiality and Availability, leading to outcomes such as Modify Memory, Read Memory, Execute Unauthorized Code or Commands and Gain Privileges or Assume Identity.

How do you prevent or mitigate Use of Pointer Subtraction to Determine Size?+

Recommended mitigations for CWE-469 include: 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.

Which programming languages are affected by Use of Pointer Subtraction to Determine Size?+

CWE-469 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-469 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-469: Use of Pointer Subtraction to Determine Size

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

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Description

Detection Methods