The product declares a critical variable, field, or member to be public when intended security policy requires it to be private.
This issue makes it more difficult to maintain the product, which indirectly affects security by making it more difficult or time-consuming to find and/or fix vulnerabilities. It also might make it easier to introduce vulnerabilities.

Primary

Indirect

Implementation

Integrity
Confidentiality
Read Application Data
Modify Application Data
Making a critical variable public allows anyone with access to the object in which the variable is contained to alter or read the value.

Other
Reduce Maintainability

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.)
High

Implementation
Data should be private, static, and final whenever possible. This will assure that your code is protected by instantiating early, preventing access, and preventing tampering.

The following example declares a critical variable public, making it accessible to anyone with access to the object in which it is contained.

public: char* password;

Instead, the critical data should be declared private.

private: char* password;

Even though this example declares the password to be private, there are other possible issues with this implementation, such as the possibility of recovering the password from process memory (CWE-257).

The following example shows a basic user account class that includes member variables for the username and password as well as a public constructor for the class and a public method to authorize access to the user account.

#define MAX_PASSWORD_LENGTH 15#define MAX_USERNAME_LENGTH 15
class UserAccount{
public:
UserAccount(char *username, char *password){if ((strlen(username) > MAX_USERNAME_LENGTH) ||(strlen(password) > MAX_PASSWORD_LENGTH)) {ExitError("Invalid username or password");}strcpy(this->username, username);strcpy(this->password, password);}

int authorizeAccess(char *username, char *password){
if ((strlen(username) > MAX_USERNAME_LENGTH) ||(strlen(password) > MAX_PASSWORD_LENGTH)) {ExitError("Invalid username or password");}
// if the username and password in the input parameters are equal to

// the username and password of this account class then authorize access
if (strcmp(this->username, username) ||strcmp(this->password, password))return 0;

// otherwise do not authorize access
elsereturn 1;

}
char username[MAX_USERNAME_LENGTH+1];char password[MAX_PASSWORD_LENGTH+1];
};

However, the member variables username and password are declared public and therefore will allow access and changes to the member variables to anyone with access to the object. These member variables should be declared private as shown below to prevent unauthorized access and changes.

class UserAccount{public:...

private:char username[MAX_USERNAME_LENGTH+1];char password[MAX_PASSWORD_LENGTH+1];};

CVE-2010-3860
variables declared public allow remote read of system properties such as user name and home directory.
https://www.cve.org/CVERecord?id=CVE-2010-3860

Failure to protect stored data from modification

OBJ01-J
Declare data members as private and provide accessible wrapper methods

SFP28
Unexpected access points

ASCMM-MNT-15

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.

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

CWE Content Team
MITRE
2009-12-28
updated Demonstrative_Examples

CWE Content Team
MITRE
2010-12-13
updated Observed_Examples

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences, Relationships, Taxonomy_Mappings

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

CWE Content Team
MITRE
2019-01-03
updated Common_Consequences, Description, Name, References, Relationships, Taxonomy_Mappings, Weakness_Ordinalities

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

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

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes, Relationships

CWE Content Team
MITRE
2023-10-26
updated Observed_Examples

CWE Content Team
MITRE
2024-02-29
4.14
2024-02-29
updated Demonstrative_Examples

Critical Variable Declared Public