What Is a Race Condition Vulnerability?

Businesses often use OWASP Top 10 as the only standard to detect security vulnerabilities. No doubt, OWASP Top 10 lists critical app security risks.

However, you will leave other flaws undetected when you solely focus on OWASP Top 10. Race condition vulnerability is one such flaw.

What is a Race Condition Vulnerability? 

Race Condition

Before defining race conditions, you need to know a few terms.

Process: Your computer assigns internal memory to run browser applications upon installation. Your system understands the execution of each browser program as a process.

Thread: Individual browser features are threads. For instance – it takes an input, searches the internet, returns output, and so on. It is a subset of and a unit of execution of processes. It shares the same internal memory assigned to the process.

Multithreading is when multiple threads are executed simultaneously. Even for simple activities, the system must process multiple threads simultaneously. For instance – even opening the browser requires multiple threads to be executed.

Multi-Processing is the parallel execution of multiple processes. This technique helps systems/ apps to work faster. How? Through the proper allocation of tasks between various processors.

Race conditions occur when a system/ device attempts to execute multiple threads concurrently. But the threads don’t get executed in the correct sequence for several reasons.

Race Condition Vulnerability

Attackers may exploit race conditions to execute malicious activities and evade security mechanisms. This is when race conditions turn into a race condition vulnerability.

For instance, to allow users to access their bank accounts online, the system must

  1. Collect their login credentials
  2. Verify it against the database
  3. Allow the user to access the account

But these instructions take place asynchronously in the multithreaded architectures of today. So, you have a race condition since these threads aren’t completed in this order.

By exploiting this race condition, cybercriminals can gain access to user accounts. They can steal data and transfer money.

What Causes Race Condition Flaws? 

Race condition security vulnerabilities are artifacts of multithreading and parallel processing. Fast-loading web pages and quicker apps are critical for business success today. A few seconds of delay will cause higher bounce rates and customer attrition.

Therefore, modern computers and apps support multithreading and parallel processing. But this ability to process multiple execution threads also creates several flaws. These flaws don’t exist in single-threaded programs and apps.

Often, developers tend to have a single-threaded mindset. So, they assume their code/ program is the only one running on the system. They also tend to assume that adjacent instructions are always executed in order. These assumptions lead to race condition vulnerabilities.

Race condition flaws also arise when developers store critical information in temporary files. Attackers may modify the temporary files or create new ones with malicious intent. This way, they can change the execution flow of the program. Or they could even exploit other flaws like buffer overflow vulnerabilities.

Based on how the program uses temporary files, the race condition attack may happen:

  • before the application runs
  • in the time lapse between legitimate read and write operations

The Anatomy of Race Condition Attacks

Sometimes, a time gap exists between a service initiating and security defenses acting. Even if the time lapse is a few seconds longer, it leads to a race condition vulnerability. Attackers exploit this flaw to flood the function/ system/ app simultaneously. This creates confusion and disrupts threads. Attackers use this for executing the following threats:

  • Deadlocks – A severe form of denial-of-service attack. Here, two or more threads must wait for one another to release a lock in a circular chain. This creates a race condition flaw. Attackers use this to bring the entire system/ app to a complete halt.
  • Thread blocks – A concurrency defect in apps/ programs. Here, one thread calls and locks an operation to prevent the progress of other threads.


  • Introduction of malicious code into systems
  • Sensitive information leakage
  • Privilege escalation
  • Illegitimate money transfers
  • Poor app/ system performance
  • Unavailability of services to legitimate users

How to Identify and Prevent Race Condition Flaws?

Identifying Race Condition Vulnerabilities

You can identify these flaws through regular testing of applications and systems. You must use the following for this testing:

  • Intelligent scanners
  • Static and dynamic testing tools
  • Manual pen-testing by trusted security partners

Prevention of Race Condition Flaws 

  • Manage and remediate race condition vulnerabilities in a proactive fashion
  • Keep educating developers on secure coding and development practices
  • Use techniques and tools for syncing threads
  • Avoid using shared states
  • Keep monitoring your systems and apps for changes and suspicious activities


Race condition vulnerabilities are well-known but rarely discovered. You must identify and secure these flaws before attackers can.