CWE-767: Access to Critical Private Variable via Public Method
Access to Critical Private Variable via Public Method
Weakness ID: 767 (Weakness Variant)
Status: Incomplete
Description
Description Summary
The software defines a public method that reads or modifies a
private variable.
Extended Description
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.
Time of Introduction
Architecture and Design
Implementation
Applicable Platforms
Languages
C++
C#
Java
Likelihood of Exploit
Low to Medium
Demonstrative Examples
Example 1
The following example declares a critical variable to be private,
and then allows the variable to be modified by public methods.
(Bad Code)
C++
private: float price;
public: void changePrice(float newPrice) {
price = newPrice;
}
Example 2
The following example could be used to implement a user forum where
a single user (UID) can switch between multiple profiles (PID).
(Bad Code)
Java
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.
Potential Mitigations
Phase
Description
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.
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.
Description
