CWE-495 Variant Draft

Private Data Structure Returned From A Public Method

This vulnerability occurs when a public method directly returns a reference to a private, internal data structure. Because the reference is live, external callers can bypass intended controls and…

Definition

What is CWE-495?

This vulnerability occurs when a public method directly returns a reference to a private, internal data structure. Because the reference is live, external callers can bypass intended controls and modify the data unexpectedly, corrupting the application's state.
This flaw breaks a core principle of encapsulation in object-oriented design. The private data structure—like an array, collection, or object—is meant to be managed solely by the class's own methods. By handing out a direct reference, you allow external code to add, remove, or alter elements without validation, leading to data corruption, security bypasses, or crashes that are difficult to debug. The fix is to return either a copy of the data (defensive copying) or an immutable view, ensuring the internal state remains protected. Identifying every instance of this pattern across a large codebase can be tedious. While SAST tools can flag the risky return statements, Plexicus uses AI to analyze the context and automatically suggest the correct remediation—such as implementing `Collections.unmodifiableList()` in Java or a slice copy in Go—saving developers hours of manual refactoring and ensuring consistent fixes.
Real-world impact

Real-world CVEs caused by CWE-495

No public CVE references are linked to this CWE in MITRE's catalog yet.

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 4

    Iterate until the response leaks data, executes attacker code, or escalates privileges.

Vulnerable code example

Vulnerable Java

Here, a public method in a Java class returns a reference to a private array. Given that arrays in Java are mutable, any modifications made to the returned reference would be reflected in the original private array.

Vulnerable Java 
private String[] colors;
  public String[] getColors() {
  	return colors;
  }
Secure code example

Secure pseudo

Secure pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist

How to prevent CWE-495

  • Implementation Declare the method private.
  • Implementation Clone the member data and keep an unmodified version of the data private to the object.
  • Implementation Use public setter methods that govern how a private member can be modified.
Detection signals

How to detect CWE-495

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.)

Plexicus auto-fix

Plexicus auto-detects CWE-495 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

Frequently asked questions

What is CWE-495?

This vulnerability occurs when a public method directly returns a reference to a private, internal data structure. Because the reference is live, external callers can bypass intended controls and modify the data unexpectedly, corrupting the application's state.

How serious is CWE-495?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-495?

MITRE lists the following affected platforms: C, C++, Java, C#.

How can I prevent CWE-495?

Declare the method private. Clone the member data and keep an unmodified version of the data private to the object.

How does Plexicus detect and fix CWE-495?

Plexicus's SAST engine matches the data-flow signature for CWE-495 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-495?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/495.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-495

CWE-664 Parent

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CWE-118 Sibling

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CWE-1229 Sibling

Creation of Emergent Resource

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CWE-1250 Sibling

Improper Preservation of Consistency Between Independent Representations of Shared State

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CWE-1329 Sibling

Reliance on Component That is Not Updateable

This vulnerability occurs when a product depends on a component that cannot be updated or patched to fix security flaws or critical bugs.

CWE-221 Sibling

Information Loss or Omission

This weakness occurs when an application fails to log critical security events or records them inaccurately, which can misguide security…

CWE-372 Sibling

Incomplete Internal State Distinction

This vulnerability occurs when an application fails to accurately track its own operational state. The system incorrectly assumes it's in…

CWE-400 Sibling

Uncontrolled Resource Consumption

This vulnerability occurs when an application fails to properly manage a finite resource, allowing an attacker to exhaust it and cause a…

CWE-404 Sibling

Improper Resource Shutdown or Release

This vulnerability occurs when a program fails to properly close or release a system resource—like a file handle, database connection, or…

Resources

Further reading

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