COMMON WEAKNESS ENUMERATIONDraft

CWE-488

Exposure of Data Element to Wrong Session

The product does not sufficiently enforce boundaries between the states of different sessions, causing data to be provided to, or used by, the wrong session.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product does not sufficiently enforce boundaries between the states of different sessions, causing data to be provided to, or used by, the wrong session.

Extended description

Data can "bleed" from one session to another through member variables of singleton objects, such as Servlets, and objects from a shared pool. In the case of Servlets, developers sometimes do not understand that, unless a Servlet implements the SingleThreadModel interface, the Servlet is a singleton; there is only one instance of the Servlet, and that single instance is used and re-used to handle multiple requests that are processed simultaneously by different threads. A common result is that developers use Servlet member fields in such a way that one user may inadvertently see another user's data. In other words, storing user data in Servlet member fields introduces a data access race condition.

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Risk

What does successful exploitation lead to?

Read Application Data

Affected security scopes: Confidentiality

Defence

How is it prevented and fixed?

Architecture and Design

Architecture and design approach

Detail
Protect the application's sessions from information leakage. Make sure that a session's data is not used or visible by other sessions.

Testing

Testing and verification approach

Detail
Use a static analysis tool to scan the code for information leakage vulnerabilities (e.g. Singleton Member Field).

Architecture and Design

Architecture and design approach

Detail
In a multithreading environment, storing user data in Servlet member fields introduces a data access race condition. Do not use member fields to store information in the Servlet.

Verification

How is it detected?

Automated Static Analysis

High
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.)