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)
Example Language: 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)
Example Language: 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: 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.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class485Insufficient Encapsulation
Development Concepts (primary)699
Research Concepts1000
ChildOfWeakness ClassWeakness Class668Exposure of Resource to Wrong Sphere
Research Concepts (primary)1000
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPFailure to protect stored data from modification
+ Maintenance Notes

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.

+ Content History
Submissions
Submission DateSubmitterOrganizationSource
2009-03-03Internal CWE Team
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