The product defines a public method that reads or modifies a private variable.
If an attacker modifies the variable to contain unexpected values, this could violate assumptions from other parts of the code. Additionally, if an attacker can read the private variable, it may expose sensitive information or make it easier to launch further attacks.

Primary

Implementation

Integrity
Other
Modify Application Data
Other

Implementation
Use class accessor and mutator methods appropriately. Perform validation when accepting data from a public method that is intended to modify a critical private variable. Also be sure that appropriate access controls are being applied when a public method interfaces with critical data.

The following example declares a critical variable to be private, and then allows the variable to be modified by public methods.

private: float price;public: void changePrice(float newPrice) {price = newPrice;}

The following example could be used to implement a user forum where a single user (UID) can switch between multiple profiles (PID).

public class Client {private int UID;public int PID;private String userName;public Client(String userName){PID = getDefaultProfileID();UID = mapUserNametoUID( userName );this.userName = userName;}public void setPID(int ID) {UID = ID;}}

The programmer implemented setPID with the intention of modifying the PID variable, but due to a typo. accidentally specified the critical variable UID instead. If the program allows profile IDs to be between 1 and 10, but a UID of 1 means the user is treated as an admin, then a user could gain administrative privileges as a result of this typo.

Failure to protect stored data from modification

SFP23
Exposed Data

OOP31-PL
Do not access private variables or subroutines in other packages
Imprecise

Allowed
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.
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.

This entry is closely associated with access control for public methods. If the public methods are restricted with proper access controls, then the information in the private variable will not be exposed to unexpected parties. There may be chaining or composite relationships between improper access controls and this weakness.

CWE Content Team
MITRE
2009-03-03
1.4
2009-05-27

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Relationships

CWE Content Team
MITRE
2014-07-30
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2017-11-08
updated Likelihood_of_Exploit, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2019-01-03
updated Taxonomy_Mappings

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2021-03-15
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated Relationships, Time_of_Introduction, Type

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Weakness_Ordinalities