CWE-421: Race Condition During Access to Alternate Channel

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-421 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-421, Race Condition During Access to Alternate Channel, 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

Make elimination of CWE-421 a product outcome

Apply CISA's Secure by Design principle of taking ownership of customer security outcomes to CWE-421, Race Condition During Access to Alternate Channel. Put the weakness in the product threat model and security roadmap, fund class-level design and platform changes, prefer safe defaults and reusable guardrails, and publish measurable progress. Do not transfer the primary burden to customer configuration when the manufacturer can remove or contain the root cause in the product.

Shifting the Balance of Cybersecurity Risk: Secure by Design Software — Cybersecurity and Infrastructure Security Agency

Connect Race Condition During Access to Alternate Channel to documented attack evidence

Recorded impacts include Gain Privileges or Assume Identity, and Bypass Protection Mechanism; observed examples include CVE-1999-0351, and CVE-2003-0230; related weaknesses include CWE-420, and CWE-362. Use these source-defined anchors to turn CWE-421 into implementation, review, and verification checks for the affected component.

CWE-421: Race Condition During Access to Alternate Channel — MITRE CWE

Apply precise root-cause mapping to CWE-421

Apply MITRE's full root-cause mapping guidance when using CWE-421, Race Condition During Access to Alternate Channel. 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-421 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-421, Race Condition During Access to Alternate Channel. 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-421: Race Condition During Access to Alternate Channel?+

CWE-421: Race Condition During Access to Alternate Channel is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product opens an alternate channel to communicate with an authorized user, but the channel is accessible to other actors. This creates a race condition that allows an attacker to access the channel before the authorized user does.

What are the security consequences of Race Condition During Access to Alternate Channel?+

If exploited, CWE-421 (Race Condition During Access to Alternate Channel) it can compromise Access Control, leading to outcomes such as Gain Privileges or Assume Identity and Bypass Protection Mechanism.

Which programming languages are affected by Race Condition During Access to Alternate Channel?+

CWE-421 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Race Condition During Access to Alternate Channel?+

MITRE documents real CVEs mapped to CWE-421, including CVE-1999-0351 and CVE-2003-0230. 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-421 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-421: Race Condition During Access to Alternate Channel

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Detection Methods

Code Examples & CVEs

Observed CVE Examples (2)

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Parent Weaknesses