Race Condition Servlet

ID

java.race_condition_servlet

Severity

high

Resource

Synchronization

Language

Java

Tags

CWE:362, NIST.SP.800-53, PCI-DSS:6.5.6

Description

Concurrent execution of servlets using shared resource with improper synchronization ('Race Condition').

Rationale

In Java servlets, race conditions arise when multiple HTTP requests are handled concurrently by different threads that access shared data without adequate synchronization.

Servlets are inherently multithreaded, processing multiple requests simultaneously unless specifically designed to synchronize access to shared resources. Without proper controls, race conditions can occur, leading to issues such as data corruption, unauthorized data access, and unpredictable application behavior.

Consider the following servlet example, which demonstrates a potential race condition:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;

public class UnsafeCounterServlet extends HttpServlet {
    private int count = 0;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        count++;
        response.getWriter().println("Current count is: " + count);
    }
}

Remediation

To remediate issues related to race conditions in Java servlets, consider the following strategies:

  1. Synchronize Access to Shared Resources: Use synchronized blocks or methods to control concurrent access to shared data, ensuring thread-safe operations.

  2. Use Concurrency Utilities: Use classes from the java.util.concurrent package, such as AtomicInteger, to handle thread-safe operations on shared resources without explicit synchronization.

  3. Minimize Shared State: Design servlets to minimize the use of shared mutable state. Prefer local variables and request-specific data to shared class-level variables.

  4. Consider Concurrency Limits: Limit the number of requests processed concurrently or use thread pools to better manage resource contention and synchronization needs.

By following these practices, race conditions in Java servlets can be effectively mitigated, ensuring consistent and secure application behavior.

References