CWE-488: Exposure of Data Element to Wrong Session

Description

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.

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.

Potential Impact

Confidentiality

Read Application Data

Demonstrative Examples

The following Servlet stores the value of a request parameter in a member field and then later echoes the parameter value to the response output stream.

Bad

public class GuestBook extends HttpServlet {
                        String name;
                           protected void doPost (HttpServletRequest req, HttpServletResponse res) {name = req.getParameter("name");...out.println(name + ", thanks for visiting!");}
                     }

While this code will work perfectly in a single-user environment, if two users access the Servlet at approximately the same time, it is possible for the two request handler threads to interleave in the following way: Thread 1: assign "Dick" to name Thread 2: assign "Jane" to name Thread 1: print "Jane, thanks for visiting!" Thread 2: print "Jane, thanks for visiting!" Thereby showing the first user the second user's name.

Mitigations & Prevention

Architecture and Design

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

Testing

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

Architecture and Design

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.

Detection Methods

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 sea

Taxonomy Mappings

7 Pernicious Kingdoms: — Data Leaking Between Users

Frequently Asked Questions

What is CWE-488?

CWE-488 (Exposure of Data Element to Wrong Session) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. 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.

How can CWE-488 be exploited?

Attackers can exploit CWE-488 (Exposure of Data Element to Wrong Session) to read application data. This weakness is typically introduced during the Implementation phase of software development.

How do I prevent CWE-488?

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

What is the severity of CWE-488?

CWE-488 is classified as a Base-level weakness (Medium abstraction). Its actual severity depends on the specific context and how the weakness manifests in your application.