CWE-488: Exposure of Data Element to 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.

Code Examples & CVEs

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.

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.

BadJava

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

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-488 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-488, Exposure of Data Element to Wrong Session, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Exposure of Data Element to Wrong Session during Architecture and Design

MITRE associates mitigation with Architecture and Design, and Testing; documented detection approaches include Automated Static Analysis; recorded impacts include Read Application Data. Use these source-defined anchors to turn CWE-488 into implementation, review, and verification checks for the affected component.

CWE-488: Exposure of Data Element to Wrong Session — MITRE CWE

Triage CWE-488 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-488, Exposure of Data Element to Wrong Session, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-488

Apply MITRE's full root-cause mapping guidance when using CWE-488, Exposure of Data Element to Wrong Session. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-488 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-488, Exposure of Data Element to Wrong Session. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-488: Exposure of Data Element to Wrong Session?+

CWE-488: Exposure of Data Element to Wrong Session is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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.

What are the security consequences of Exposure of Data Element to Wrong Session?+

If exploited, CWE-488 (Exposure of Data Element to Wrong Session) it can compromise Confidentiality, leading to outcomes such as Read Application Data.

How do you prevent or mitigate Exposure of Data Element to Wrong Session?+

Recommended mitigations for CWE-488 include: 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 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.

Which programming languages are affected by Exposure of Data Element to Wrong Session?+

CWE-488 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-488 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-488: Exposure of Data Element to Wrong Session

Extended Description

Technical Details

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Mitigation Strategies

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Detection Methods

Code Examples & CVEs

Demonstrative Examples

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-488 with SSDF evidence

Address Exposure of Data Element to Wrong Session during Architecture and Design

Triage CWE-488 against known exploitation evidence

Apply precise root-cause mapping to CWE-488

Validate CWE-488 with root-cause mapping checks

Frequently Asked Questions

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