CWE-638: Not Using Complete Mediation

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The product does not perform access checks on a resource every time the resource is accessed by an entity, which can create resultant weaknesses if that entity's rights or privileges change over time.

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Technical Details

Structure
Simple

Applicable To

Languages
Not Language-Specific
Platforms

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-638 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-638, Not Using Complete Mediation, 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 Not Using Complete Mediation during Architecture and Design

MITRE associates mitigation with Architecture and Design; recorded impacts include Gain Privileges or Assume Identity, Execute Unauthorized Code or Commands, Bypass Protection Mechanism, Read Application Data, and Other; the entry maps to CAPEC-104. Use these source-defined anchors to turn CWE-638 into implementation, review, and verification checks for the affected component.

CWE-638: Not Using Complete Mediation — MITRE CWE

Triage CWE-638 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-638, Not Using Complete Mediation, 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-638

Apply MITRE's full root-cause mapping guidance when using CWE-638, Not Using Complete Mediation. 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-638 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-638, Not Using Complete Mediation. 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-638: Not Using Complete Mediation?+

CWE-638: Not Using Complete Mediation is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product does not perform access checks on a resource every time the resource is accessed by an entity, which can create resultant weaknesses if that entity's rights or privileges change over time.

What are the security consequences of Not Using Complete Mediation?+

If exploited, CWE-638 (Not Using Complete Mediation) it can compromise Integrity, Confidentiality, Availability, Access Control and Other, leading to outcomes such as Gain Privileges or Assume Identity, Execute Unauthorized Code or Commands, Bypass Protection Mechanism, Read Application Data and Other.

How do you prevent or mitigate Not Using Complete Mediation?+

Recommended mitigations for CWE-638 include: Invalidate cached privileges, file handles or descriptors, or other access credentials whenever identities, processes, policies, roles, capabilities or permissions change. Perform complete authentication checks before accepting, caching and reusing data, dynamic content and code (scripts). Avoid caching access control decisions as much as possible. Identify all possible code paths that might access sensitive resources. If possible, create and use a single interface that performs the access checks, and develop code standards that require use of this interface.

Which programming languages are affected by Not Using Complete Mediation?+

CWE-638 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 Not Using Complete Mediation?+

MITRE documents real CVEs mapped to CWE-638, including CVE-2007-0408. 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-638 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.

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