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Home > CWE List > CWE-469: Use of Pointer Subtraction to Determine Size (4.18)
ID
CWE Glossary Definition

CWE-469: Use of Pointer Subtraction to Determine Size

Weakness ID: 469
Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: Base Base - 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.
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Description
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.
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.
Impact Details

Modify Memory; Read Memory; Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity

Scope: Access Control, Integrity, Confidentiality, Availability

There is the potential for arbitrary code execution with privileges of the vulnerable program.
Potential Mitigations
Phase(s) Mitigation

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.
Relationships
Section Help This 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" (View-1000)
Nature Type ID Name
ChildOf Pillar Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things. 682 Incorrect Calculation
Relevant to the view "Software Development" (View-699)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 465 Pointer Issues
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.
Phase Note
Implementation
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.
Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

Likelihood Of Exploit
Medium
Demonstrative Examples

Example 1


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.

(bad code)
Example Language: C
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
...

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.

(good code)
Example Language: C

...

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


Detection Methods
Method Details

Fuzzing
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.

Effectiveness: High

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.
Nature Type ID Name
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 740 CERT C Secure Coding Standard (2008) Chapter 7 - Arrays (ARR)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 874 CERT C++ Secure Coding Section 06 - Arrays and the STL (ARR)
MemberOf ViewView - 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). 884 CWE Cross-section
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 971 SFP Secondary Cluster: Faulty Pointer Use
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1160 SEI CERT C Coding Standard - Guidelines 06. Arrays (ARR)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1408 Comprehensive Categorization: Incorrect Calculation
Vulnerability Mapping Notes
Usage ALLOWED
(this CWE ID may be used to map to real-world vulnerabilities)
Reason Acceptable-Use

Rationale

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
CLASP Improper pointer subtraction
CERT C Secure Coding ARR36-C Exact Do not subtract or compare two pointers that do not refer to the same array
Software Fault Patterns SFP7 Faulty Pointer Use
References
[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005.
<https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>. (URL validated: 2024年11月17日)
Content History
Submissions
Submission Date Submitter Organization
2006年07月19日
(CWE Draft 3, 2006年07月19日) 		CLASP
Modifications
Modification Date Modifier Organization
2023年06月29日 CWE Content Team MITRE
updated Mapping_Notes
2023年04月27日 CWE Content Team MITRE
updated Detection_Factors, Relationships
2023年01月31日 CWE Content Team MITRE
updated Description
2022年10月13日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2021年03月15日 CWE Content Team MITRE
updated Potential_Mitigations
2020年06月25日 CWE Content Team MITRE
updated Common_Consequences
2020年02月24日 CWE Content Team MITRE
updated References, Relationships, Taxonomy_Mappings
2019年01月03日 CWE Content Team MITRE
updated Relationships
2017年11月08日 CWE Content Team MITRE
updated Demonstrative_Examples, Taxonomy_Mappings, White_Box_Definitions
2014年07月30日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2014年06月23日 CWE Content Team MITRE
updated Other_Notes
2014年02月18日 CWE Content Team MITRE
updated Potential_Mitigations
2012年10月30日 CWE Content Team MITRE
updated Demonstrative_Examples, Potential_Mitigations
2012年05月11日 CWE Content Team MITRE
updated Relationships
2011年09月13日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2011年06月01日 CWE Content Team MITRE
updated Common_Consequences
2008年11月24日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2008年09月08日 CWE Content Team MITRE
updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2008年08月01日 KDM Analytics
added/updated white box definitions
2008年07月01日 Eric Dalci Cigital
updated Time_of_Introduction
Previous Entry Names
Change Date Previous Entry Name
2008年04月11日 Improper Pointer Subtraction
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Page Last Updated: September 09, 2025

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