CWE-572 Variant Draft

Call to Thread run() instead of start()

This vulnerability occurs when a program incorrectly calls a thread's `run()` method directly, instead of using the `start()` method. This mistake causes the thread's code to execute within the…

Definition

What is CWE-572?

This vulnerability occurs when a program incorrectly calls a thread's `run()` method directly, instead of using the `start()` method. This mistake causes the thread's code to execute within the caller's current thread, bypassing the creation of a new, concurrent thread of execution.
Calling `run()` directly is almost always a programming error. The developer's intent is to launch new, concurrent operations using the `Thread` class. However, by calling `run()`, the code within that method simply executes as a normal function call in the existing thread. This defeats the entire purpose of using threads, leading to sequential execution and potential performance issues, as no true parallelism or concurrency is achieved. The core issue is a misunderstanding of the Java threading model. The `start()` method is responsible for the native OS-level thread creation and scheduling, which then automatically calls the `run()` method in the new thread context. Bypassing `start()` means the `run()` method's code runs with the stack and context of the parent thread, which can cause unexpected behavior, block the UI, or break assumptions about thread-local data and synchronization.
Real-world impact

Real-world CVEs caused by CWE-572

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

The following excerpt from a Java program mistakenly calls run() instead of start().

Vulnerable Java 
Thread thr = new Thread() {
  	public void run() {
  		...
  	}
  };
  thr.run();
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-572

  • Implementation Use the start() method instead of the run() method.
Detection signals

How to detect CWE-572

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-572 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-572?

This vulnerability occurs when a program incorrectly calls a thread's `run()` method directly, instead of using the `start()` method. This mistake causes the thread's code to execute within the caller's current thread, bypassing the creation of a new, concurrent thread of execution.

How serious is CWE-572?

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-572?

MITRE lists the following affected platforms: Java.

How can I prevent CWE-572?

Use the start() method instead of the run() method.

How does Plexicus detect and fix CWE-572?

Plexicus's SAST engine matches the data-flow signature for CWE-572 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-572?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/572.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-572

CWE-821 Parent

Incorrect Synchronization

This vulnerability occurs when multiple parts of a program, such as threads or processes, access a shared resource like a variable, file,…

CWE-1088 Sibling

Synchronous Access of Remote Resource without Timeout

This vulnerability occurs when an application makes a synchronous call to a remote service or resource but does not set a timeout, or sets…

CWE-1264 Sibling

Hardware Logic with Insecure De-Synchronization between Control and Data Channels

This vulnerability occurs when a hardware design incorrectly forwards data before its security or permission checks have finished…

CWE-574 Sibling

EJB Bad Practices: Use of Synchronization Primitives

This vulnerability occurs when an Enterprise JavaBeans (EJB) component improperly uses thread synchronization primitives, violating the…

Resources

Further reading

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