CWE-1090 Base Incomplete

Method Containing Access of a Member Element from Another Class

This weakness occurs when a method in one class directly accesses a private or internal member (like a field or property) of a different class, bypassing proper interfaces.

Definition

What is CWE-1090?

This weakness occurs when a method in one class directly accesses a private or internal member (like a field or property) of a different class, bypassing proper interfaces.
Directly reaching into another class's internals breaks a core principle of object-oriented design: encapsulation. It creates tight, hidden couplings between classes, making your code brittle and difficult to change. When a class's internal state can be changed from many unexpected places, it becomes hard to reason about its behavior, track data flow, and ensure integrity, which sets the stage for bugs. From a security perspective, this poor structure doesn't directly cause a vulnerability but significantly increases risk. It makes the codebase harder to audit and maintain, slowing down the identification and fixing of actual security flaws. Furthermore, this pattern often bypasses validation logic, allowing data to be set to invalid or dangerous states, and it makes introducing new vulnerabilities during future modifications much more likely.
Real-world impact

Real-world CVEs caused by CWE-1090

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 pseudo

MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.

Vulnerable pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
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-1090

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Detection signals

How to detect CWE-1090

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-1090 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-1090?

This weakness occurs when a method in one class directly accesses a private or internal member (like a field or property) of a different class, bypassing proper interfaces.

How serious is CWE-1090?

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-1090?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-1090?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

How does Plexicus detect and fix CWE-1090?

Plexicus's SAST engine matches the data-flow signature for CWE-1090 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-1090?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1090.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-1090

CWE-1061 Parent

Insufficient Encapsulation

This weakness occurs when a software component exposes too much of its internal workings, such as data structures or implementation logic.…

CWE-1054 Sibling

Invocation of a Control Element at an Unnecessarily Deep Horizontal Layer

This weakness occurs when code in one architectural layer directly calls functions or methods in a much deeper layer, skipping over the…

CWE-1057 Sibling

Data Access Operations Outside of Expected Data Manager Component

This weakness occurs when an application bypasses its dedicated, central data manager component and performs data access operations…

CWE-1062 Sibling

Parent Class with References to Child Class

This weakness occurs when a parent class directly references its child classes, their methods, or their member variables, creating a…

CWE-1083 Sibling

Data Access from Outside Expected Data Manager Component

This weakness occurs when an application is designed to handle all data operations through a dedicated manager component (like a database…

CWE-1100 Sibling

Insufficient Isolation of System-Dependent Functions

This weakness occurs when an application fails to separate its core logic from functions that depend on a specific operating system,…

CWE-1105 Sibling

Insufficient Encapsulation of Machine-Dependent Functionality

This weakness occurs when an application relies on hardware-specific or platform-dependent features but fails to isolate that code from…

CWE-766 Sibling

Critical Data Element Declared Public

This vulnerability occurs when a critical piece of data—like a variable, field, or class member—is mistakenly declared as public when it…

Resources

Further reading

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