CWE-488: Exposure of Data Element to Wrong Session
Exposure of Data Element to Wrong Session
Weakness ID: 488 (Weakness Variant)
Status: Draft
Description
Description Summary
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.
Time of Introduction
Implementation
Applicable Platforms
Languages
All
Common Consequences
Scope
Effect
Confidentiality
Technical Impact: Read application
data
Demonstrative Examples
Example 1
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.
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.
Potential Mitigations
Phase: 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.
Phase: Testing
Use a static analysis tool to scan the code for information leakage
vulnerabilities (e.g. Singleton Member Field).
Phase: 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.
Description
