The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.

This can have security implications when the expected synchronization is in security-critical code, such as recording whether a user is authenticated or modifying important state information that should not be influenced by an outsider.

A race condition occurs within concurrent environments, and is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc.

A race condition violates these properties, which are closely related:

• Exclusivity - the code sequence is given exclusive access to the shared resource, i.e., no other code sequence can modify properties of the shared resource before the original sequence has completed execution.
• Atomicity - the code sequence is behaviorally atomic, i.e., no other thread or process can concurrently execute the same sequence of instructions (or a subset) against the same resource.

A race condition exists when an "interfering code sequence" can still access the shared resource, violating exclusivity. Programmers may assume that certain code sequences execute too quickly to be affected by an interfering code sequence; when they are not, this violates atomicity. For example, the single "x++" statement may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read (the original value of x), followed by a computation (x+1), followed by a write (save the result to x).

The interfering code sequence could be "trusted" or "untrusted." A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Modes Of Introduction

Architecture and Design
Implementation

Applicable Platforms

Language

Name: C (Sometimes)
Name: C++ (Sometimes)
Name: Java (Sometimes)

Technologies

Class: Mobile (Undetermined)
Class: ICS/OT (Undetermined)

Common Consequences

Observed Examples

Potential Mitigations

Phases : Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Phases : Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Phases : Architecture and Design

Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.

Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Phases : Implementation
When using multithreading and operating on shared variables, only use thread-safe functions.
Phases : Implementation
Use atomic operations on shared variables. Be wary of innocent-looking constructs such as "x++". This may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read, followed by a computation, followed by a write.
Phases : Implementation
Use a mutex if available, but be sure to avoid related weaknesses such as CWE-412.
Phases : Implementation
Avoid double-checked locking (CWE-609) and other implementation errors that arise when trying to avoid the overhead of synchronization.
Phases : Implementation
Disable interrupts or signals over critical parts of the code, but also make sure that the code does not go into a large or infinite loop.
Phases : Implementation
Use the volatile type modifier for critical variables to avoid unexpected compiler optimization or reordering. This does not necessarily solve the synchronization problem, but it can help.
Phases : Architecture and Design // Operation
Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Detection Methods

Black Box

Black box methods may be able to identify evidence of race conditions via methods such as multiple simultaneous connections, which may cause the software to become instable or crash. However, race conditions with very narrow timing windows would not be detectable.

White Box

Common idioms are detectable in white box analysis, such as time-of-check-time-of-use (TOCTOU) file operations (CWE-367), or double-checked locking (CWE-609).

Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Race conditions may be detected with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior.

Insert breakpoints or delays in between relevant code statements to artificially expand the race window so that it will be easier to detect.

Effectiveness : Moderate

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Effectiveness : High

Dynamic Analysis with Automated Results Interpretation

According to SOAR, the following detection techniques may be useful:

Effectiveness : SOAR Partial

Dynamic Analysis with Manual Results Interpretation

According to SOAR, the following detection techniques may be useful:

Effectiveness : High

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Effectiveness : High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Effectiveness : High

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Effectiveness : High

Vulnerability Mapping Notes

Rationale : This CWE entry is a Class and might have Base-level children that would be more appropriate
Comments : Examine children of this entry to see if there is a better fit

Related Attack Patterns

Notes

The relationship between race conditions and synchronization problems (CWE-662) needs to be further developed. They are not necessarily two perspectives of the same core concept, since synchronization is only one technique for avoiding race conditions, and synchronization can be used for other purposes besides race condition prevention.
Race conditions in web applications are under-studied and probably under-reported. However, in 2008 there has been growing interest in this area.
Much of the focus of race condition research has been in Time-of-check Time-of-use (TOCTOU) variants (CWE-367), but many race conditions are related to synchronization problems that do not necessarily require a time-of-check.
From a classification/taxonomy perspective, the relationships between concurrency and program state need closer investigation and may be useful in organizing related issues.

References

REF-44

24 Deadly Sins of Software Security
Michael Howard, David LeBlanc, John Viega.

REF-349

volatile - Multithreaded Programmer's Best Friend
Andrei Alexandrescu.
https://drdobbs.com/cpp/volatile-the-multithreaded-programmers-b/184403766

REF-350

Thread-safe webapps using Spring
Steven Devijver.
https://web.archive.org/web/20170609174845/http://www.javalobby.org/articles/thread-safe/index.jsp

REF-351

Prevent race conditions
David Wheeler.
https://www.ida.liu.se/~TDDC90/literature/papers/SP-race-conditions.pdf

REF-352

Race Conditions, Files, and Security Flaws; or the Tortoise and the Hare Redux
Matt Bishop.
https://seclab.cs.ucdavis.edu/projects/vulnerabilities/scriv/ucd-ecs-95-08.pdf

REF-353

Secure Programming for Linux and Unix HOWTO
David Wheeler.
https://dwheeler.com/secure-programs/Secure-Programs-HOWTO/avoid-race.html

REF-354

Discovering and Exploiting Named Pipe Security Flaws for Fun and Profit
Blake Watts.
https://www.blakewatts.com/blog/discovering-and-exploiting-named-pipe-security-flaws-for-fun-and-profit

REF-355

On Race Vulnerabilities in Web Applications
Roberto Paleari, Davide Marrone, Danilo Bruschi, Mattia Monga.
http://security.dico.unimi.it/~roberto/pubs/dimva08-web.pdf

REF-356

Avoiding Race Conditions and Insecure File Operations
https://web.archive.org/web/20081010155022/http://developer.apple.com/documentation/Security/Conceptual/SecureCodingGuide/Articles/RaceConditions.html

REF-357

Top 25 Series - Rank 25 - Race Conditions
Johannes Ullrich.
https://web.archive.org/web/20100530231203/http://blogs.sans.org:80/appsecstreetfighter/2010/03/26/top-25-series-rank-25-race-conditions/

REF-76

Least Privilege
Sean Barnum, Michael Gegick.
https://web.archive.org/web/20211209014121/https://www.cisa.gov/uscert/bsi/articles/knowledge/principles/least-privilege

REF-1237

Intel BIOS locking mechanism contains race condition that enables write protection bypass
CERT Coordination Center.
https://www.kb.cert.org/vuls/id/766164/

Submission

Modifications