CWE-493 Variant Draft High likelihood

Critical Public Variable Without Final Modifier

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.

Definition

What is CWE-493?

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.
When a critical variable—like a security flag, configuration setting, or cryptographic key—is made public without the `final` modifier, any part of the application with access to its class can alter its contents. This breaks the intended design and can lead to security failures, as other components may rely on that value remaining constant after being set. Manually tracking these exposed variables across a large codebase is challenging. An ASPM like Plexicus can automatically detect this pattern via SAST, and its AI remediation engine can suggest the specific code change—such as adding the `final` keyword or refactoring to a private field—saving significant manual review time and reducing risk.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-493

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

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    Suppose this WidgetData class is used for an e-commerce web site. The programmer attempts to prevent price-tampering attacks by setting the price of the widget using the constructor.

  2. 2

    The price field is not final. Even though the value is set by the constructor, it could be modified by anybody that has access to an instance of WidgetData.

  3. 3

    Assume the following code is intended to provide the location of a configuration file that controls execution of the application.

  4. 4

    While this field is readable from any function, and thus might allow an information leak of a pathname, a more serious problem is that it can be changed by any function.

Verwundbares Codebeispiel

Vulnerable Java

Suppose this WidgetData class is used for an e-commerce web site. The programmer attempts to prevent price-tampering attacks by setting the price of the widget using the constructor.

Verwundbar Java 
public final class WidgetData extends Applet {
  	public float price;
  	...
  	public WidgetData(...) {
  		this.price = LookupPrice("MyWidgetType");
  	}
  }
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-493

  • Implementation Declare all public fields as final when possible, especially if it is used to maintain internal state of an Applet or of classes used by an Applet. If a field must be public, then perform all appropriate sanity checks before accessing the field from your code.
Erkennungssignale

How to detect CWE-493

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 erkennt CWE-493 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-493?

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.

Wie gravierend ist CWE-493?

MITRE stuft die Exploit-Wahrscheinlichkeit als hoch ein — diese Schwachstelle wird aktiv in freier Wildbahn ausgenutzt und sollte priorisiert behoben werden.

Welche Sprachen oder Plattformen sind von CWE-493 betroffen?

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

Wie kann ich CWE-493 verhindern?

Declare all public fields as final when possible, especially if it is used to maintain internal state of an Applet or of classes used by an Applet. If a field must be public, then perform all appropriate sanity checks before accessing the field from your code.

Wie erkennt und behebt Plexicus CWE-493?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-493 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-493?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/493.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-493

CWE-668 Parent

Exposure of Resource to Wrong Sphere

This vulnerability occurs when an application unintentionally makes a resource accessible to users or systems that should not have…

CWE-1189 Sibling

Improper Isolation of Shared Resources on System-on-a-Chip (SoC)

This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly separate shared hardware resources between secure (trusted) and…

CWE-1282 Sibling

Assumed-Immutable Data is Stored in Writable Memory

This vulnerability occurs when data that should be permanent and unchangeable—like a bootloader, device IDs, or one-time configuration…

CWE-1327 Sibling

Binding to an Unrestricted IP Address

This vulnerability occurs when software or a service is configured to bind to the IP address 0.0.0.0 (or :: in IPv6), which acts as a…

CWE-1331 Sibling

Improper Isolation of Shared Resources in Network On Chip (NoC)

This vulnerability occurs when a Network on Chip (NoC) fails to properly separate its internal, shared resources—like buffers, switches,…

CWE-134 Sibling

Use of Externally-Controlled Format String

This vulnerability occurs when a program uses a format string from an untrusted, external source (like user input, a network packet, or a…

CWE-200 Sibling

Exposure of Sensitive Information to an Unauthorized Actor

This weakness occurs when an application unintentionally reveals sensitive data to someone who shouldn't have access to it.

CWE-374 Sibling

Passing Mutable Objects to an Untrusted Method

This vulnerability occurs when a function receives a direct reference to mutable data, such as an object or array, instead of a safe copy…

CWE-375 Sibling

Returning a Mutable Object to an Untrusted Caller

This vulnerability occurs when a method directly returns a reference to its internal mutable data, allowing untrusted calling code to…

Ressourcen

Further reading

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