Race Conditions Attack Led To limit bypass €€€

Jay Sharma
3 min readJul 7, 2024


Race conditions are not only a source of software bugs but can also be exploited by attackers to compromise the security and integrity of a system. In this blog post, we’ll delve into what race condition attacks are, how they occur, and what you can do to protect your systems against them.

What is a Race Condition Attack?

A race condition attack occurs when an attacker exploits the time-sensitive nature of race conditions to manipulate the execution flow of a program, leading to unauthorized actions, data corruption, or other malicious outcomes. By carefully timing their actions, attackers can gain privileges, alter data, or cause a denial of service.

How Do Race Condition Attacks Occur?

Race condition attacks exploit the small window of time during which a shared resource is accessed by multiple threads or processes. Here are some typical scenarios:

  1. TOCTOU (Time of Check to Time of Use): This classic race condition attack involves exploiting the gap between checking a condition and using the result. For example, an attacker might replace a file between the time a program checks its permissions and the time it opens the file.
  2. Incrementing a Shared Counter: Attackers might manipulate counters or shared variables in a multi-threaded environment, causing the program to behave incorrectly or allocate resources improperly.
  3. Privilege Escalation: By exploiting race conditions in systems that handle user permissions, attackers can elevate their privileges and gain unauthorized access to restricted areas of the system.

Real-World Examples of Race Condition Attacks

1. OpenSSL’s Heartbleed Bug: While not a traditional race condition, the Heartbleed vulnerability exploited a timing-related flaw in OpenSSL’s handling of heartbeat requests, leading to information leakage.

2. Android Vulnerability (CVE-2014–3153): This bug in the Android kernel allowed attackers to gain root privileges by exploiting a race condition in the futex subsystem.

Personal Experience: Exploiting a Race Condition in a Bug Bounty Program

In one of my bug bounty hunting experiences, I encountered a race condition in a system that provided limited resources to users. By exploiting the race condition, I was able to exceed the allocated resource limits. This issue had significant implications for the system’s resource management and stability. For reporting this vulnerability, I received a bounty of €150. This experience highlighted the real-world impact of race condition vulnerabilities and the importance of robust concurrency handling. Further more also found race condition in different Application testing.

Here is methodology I followed https://portswigger.net/web-security/race-conditions#methodology

Preventing Race Condition Attacks

Preventing race condition attacks involves careful design and implementation of concurrent systems. Here are some strategies:

  1. Proper Synchronization: Use mutexes, semaphores, and other primitives to control access to shared resources.
  2. Atomic Operations: Leverage atomic operations that complete in a single step, making it impossible for an attacker to interrupt the process.
  3. Avoid Shared State: Design your systems to minimize or eliminate shared state, reducing the risk of race conditions.
  4. Code Reviews and Testing: Conduct thorough code reviews and use tools like static analyzers and dynamic testing frameworks to identify potential race conditions.


Race condition attacks are a significant threat in concurrent programming, but with careful design and implementation, you can mitigate these risks. Understanding how race conditions occur and adopting best practices for synchronization and resource management will help you build more secure and robust systems.

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