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.
Real-world impact

Real-world CVEs caused by CWE-493

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

    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.

Vulnerable code example

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.

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

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 auto-detects CWE-493 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-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.

How serious is CWE-493?

MITRE rates the likelihood of exploit as High — this weakness is actively exploited in the wild and should be prioritized for remediation.

What languages or platforms are affected by CWE-493?

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

How can I prevent CWE-493?

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.

How does Plexicus detect and fix CWE-493?

Plexicus's SAST engine matches the data-flow signature for CWE-493 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-493?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/493.html. You can also reference OWASP and NIST documentation for adjacent guidance.

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Weaknesses related to CWE-493

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CWE-1331 Sibling

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CWE-134 Sibling

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CWE-200 Sibling

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CWE-374 Sibling

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