CWE-543 Variant Incomplete

Use of Singleton Pattern Without Synchronization in a Multithreaded Context

This vulnerability occurs when a singleton pattern is implemented in a multithreaded application without proper synchronization, potentially leading to multiple instances or corrupted state.

Definition

What is CWE-543?

This vulnerability occurs when a singleton pattern is implemented in a multithreaded application without proper synchronization, potentially leading to multiple instances or corrupted state.
The singleton pattern is designed to ensure only one instance of a class exists. However, in a multithreaded environment, if the creation of that instance is not properly synchronized, multiple threads can simultaneously pass the instance check and create their own copies. This breaks the fundamental guarantee of the pattern and leads to unpredictable application behavior. To prevent this, developers must implement thread-safe initialization. Common solutions include using synchronized blocks during creation, employing eager initialization at class-load time, or leveraging language-specific constructs like atomic references or initialization-on-demand holder idioms. The correct approach depends on your performance requirements and programming language, but ignoring synchronization is not an option in concurrent code.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-543

Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    This method is part of a singleton pattern, yet the following singleton() pattern is not thread-safe. It is possible that the method will create two objects instead of only one.

  2. 2

    Consider the following course of events:

  3. 3

    - Thread A enters the method, finds singleton to be null, begins the NumberConverter constructor, and then is swapped out of execution. - Thread B enters the method and finds that singleton remains null. This will happen if A was swapped out during the middle of the constructor, because the object reference is not set to point at the new object on the heap until the object is fully initialized. - Thread B continues and constructs another NumberConverter object and returns it while exiting the method. - Thread A continues, finishes constructing its NumberConverter object, and returns its version.

  4. 4

    At this point, the threads have created and returned two different objects.

Verwundbares Codebeispiel

Vulnerable Java

This method is part of a singleton pattern, yet the following singleton() pattern is not thread-safe. It is possible that the method will create two objects instead of only one.

Verwundbar Java 
private static NumberConverter singleton;
  public static NumberConverter get_singleton() {
  	if (singleton == null) {
  		singleton = new NumberConverter();
  	}
  	return singleton;
  }
Sicheres Codebeispiel

Secure pseudo

Sicher 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.
Präventions-Checkliste

How to prevent CWE-543

  • Architecture and Design Use the Thread-Specific Storage Pattern. See References.
  • Implementation Do not use member fields to store information in the Servlet. In multithreading environments, storing user data in Servlet member fields introduces a data access race condition.
  • Implementation Avoid using the double-checked locking pattern in language versions that cannot guarantee thread safety. This pattern may be used to avoid the overhead of a synchronized call, but in certain versions of Java (for example), this has been shown to be unsafe because it still introduces a race condition (CWE-209).
Erkennungssignale

How to detect CWE-543

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-543 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen
Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-543?

This vulnerability occurs when a singleton pattern is implemented in a multithreaded application without proper synchronization, potentially leading to multiple instances or corrupted state.

Wie gravierend ist CWE-543?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-543 betroffen?

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

Wie kann ich CWE-543 verhindern?

Use the Thread-Specific Storage Pattern. See References. Do not use member fields to store information in the Servlet. In multithreading environments, storing user data in Servlet member fields introduces a data access race condition.

Wie erkennt und behebt Plexicus CWE-543?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-543 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-543?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/543.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-543

CWE-820 Parent

Missing Synchronization

This vulnerability occurs when multiple parts of your application (like threads or processes) use the same resource—such as a variable,…

CWE-1096 Sibling

Singleton Class Instance Creation without Proper Locking or Synchronization

This flaw occurs when a Singleton class is implemented without proper thread-safe controls, allowing multiple instances to be created in…

CWE-567 Sibling

Unsynchronized Access to Shared Data in a Multithreaded Context

This vulnerability occurs when multiple threads in an application can read and modify shared data, like static variables, without proper…

Ressourcen

Further reading

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