CWE-366: Race Condition within a Thread

Code Examples & CVEs

Demonstrative Examples

The following example demonstrates the weakness.

BadC

int foo = 0;int storenum(int num) {static int counter = 0;counter++;if (num > foo) foo = num;return foo;}

The following example demonstrates the weakness.

BadJava

public classRace {                         static int foo = 0;public static void main() {                                                                 new Threader().start();foo = 1;                            }public static class Threader extends Thread {                                                                 public void run() {System.out.println(foo);}                            }                      }

Observed CVE Examples (1)

CVE-2022-2621

Chain: two threads in a web browser use the same resource (CWE-366), but one of those threads can destroy the resource before the other has completed (CWE-416).

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Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-366 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-366, Race Condition within a Thread, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Race Condition within a Thread during Architecture and Design

MITRE associates mitigation with Architecture and Design; documented detection approaches include Automated Static Analysis; recorded impacts include Alter Execution Logic, and Unexpected State. Use these source-defined anchors to turn CWE-366 into implementation, review, and verification checks for the affected component.

CWE-366: Race Condition within a Thread — MITRE CWE

Triage CWE-366 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-366, Race Condition within a Thread, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-366

Apply MITRE's full root-cause mapping guidance when using CWE-366, Race Condition within a Thread. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-366 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-366, Race Condition within a Thread. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-366: Race Condition within a Thread?+

CWE-366: Race Condition within a Thread is a Common Weakness Enumeration (CWE) entry maintained by MITRE. If two threads of execution use a resource simultaneously, there exists the possibility that resources may be used while invalid, in turn making the state of execution undefined.

What are the security consequences of Race Condition within a Thread?+

If exploited, CWE-366 (Race Condition within a Thread) it can compromise Integrity and Other, leading to outcomes such as Alter Execution Logic and Unexpected State.

How do you prevent or mitigate Race Condition within a Thread?+

Recommended mitigations for CWE-366 include: Use locking functionality. This is the recommended solution. Implement some form of locking mechanism around code which alters or reads persistent data in a multithreaded environment. Create resource-locking validation checks. If no inherent locking mechanisms exist, use flags and signals to enforce your own blocking scheme when resources are being used by other threads of execution.

Which programming languages are affected by Race Condition within a Thread?+

CWE-366 commonly affects C, C++, Java and C#. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Race Condition within a Thread?+

MITRE documents real CVEs mapped to CWE-366, including CVE-2022-2621. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-366 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-366: Race Condition within a Thread

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

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Description