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Home > CWE List > CWE- Individual Dictionary Definition (4.14)  

CWE-495: Private Data Structure Returned From A Public Method

Weakness ID: 495
Vulnerability Mapping: ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities
Abstraction: VariantVariant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.
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+ Description
The product has a method that is declared public, but returns a reference to a private data structure, which could then be modified in unexpected ways.
+ Relationships
Section HelpThis 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" (CWE-1000)
ChildOfPillarPillar - 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.664Improper Control of a Resource Through its Lifetime
+ 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.
+ 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.


C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

Java (Undetermined Prevalence)

C# (Undetermined Prevalence)

+ 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.

Technical Impact: Modify Application Data

The contents of the data structure can be modified from outside the intended scope.
+ Demonstrative Examples

Example 1

Here, a public method in a Java class returns a reference to a private array. Given that arrays in Java are mutable, any modifications made to the returned reference would be reflected in the original private array.

(bad code)
Example Language: Java 
private String[] colors;
public String[] getColors() {
return colors;

Example 2

In this example, the Color class defines functions that return non-const references to private members (an array type and an integer type), which are then arbitrarily altered from outside the control of the class.

(bad code)
Example Language: C++ 
class Color
int[2] colorArray;
int colorValue;
Color () : colorArray { 1, 2 }, colorValue (3) { };
int[2] & fa () { return colorArray; } // return reference to private array
int & fv () { return colorValue; } // return reference to private integer

int main ()
Color c;

c.fa () [1] = 42; // modifies private array element
c.fv () = 42; // modifies private int

return 0;
+ Potential Mitigations

Phase: Implementation

Declare the method private.

Phase: Implementation

Clone the member data and keep an unmodified version of the data private to the object.

Phase: Implementation

Use public setter methods that govern how a private member can be modified.
+ Detection Methods

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.
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.4857PK - Encapsulation
MemberOfViewView - 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).884CWE Cross-section
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.963SFP Secondary Cluster: Exposed Data
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1416Comprehensive Categorization: Resource Lifecycle Management
+ Vulnerability Mapping Notes


(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use


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


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 NameNode IDFitMapped Node Name
7 Pernicious KingdomsPrivate Array-Typed Field Returned From A Public Method
Software Fault PatternsSFP23Exposed Data
+ References
[REF-6] Katrina Tsipenyuk, Brian Chess and Gary McGraw. "Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors". NIST Workshop on Software Security Assurance Tools Techniques and Metrics. NIST. 2005-11-07. <>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
(CWE Draft 3, 2006-07-19)
7 Pernicious Kingdoms
+ Modifications
Modification DateModifierOrganization
2008-07-01Sean EidemillerCigital
added/updated demonstrative examples
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-08-01KDM Analytics
added/updated white box definitions
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Relationships, Taxonomy_Mappings
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Common_Consequences, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Relationships, White_Box_Definitions
2019-01-03CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Description, Name, Potential_Mitigations
2020-02-24CWE Content TeamMITRE
updated References, Relationships
2023-04-27CWE Content TeamMITRE
updated Detection_Factors, Relationships
2023-06-29CWE Content TeamMITRE
updated Mapping_Notes
+ Previous Entry Names
Change DatePrevious Entry Name
2019-01-03Private Array-Typed Field Returned From A Public Method
Page Last Updated: February 29, 2024