Data Leak Between Sessions
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

+ 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.

(Bad Code)
Example Language: Java 
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.

+ Potential Mitigations

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

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

In 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.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class485Insufficient Encapsulation
Development Concepts (primary)699
Seven Pernicious Kingdoms (primary)700
Research Concepts (primary)1000
PeerOfWeakness BaseWeakness Base567Unsynchronized Access to Shared Data
Research Concepts1000
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsData Leaking Between Users
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
59Session Credential Falsification through Prediction
60Reusing Session IDs (aka Session Replay)
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
7 Pernicious KingdomsExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential Mitigations, Time of Introduction
2008-09-08CWE Content TeamMITREInternal
updated Description, Relationships, Other Notes, Taxonomy Mappings
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative Examples
2009-10-29CWE Content TeamMITREInternal
updated Description, Other Notes
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Data Leaking Between Users
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