CWE-637: Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')

Extended Description

Security mechanisms should be as simple as possible. Complex security mechanisms may engender partial implementations and compatibility problems, with resulting mismatches in assumptions and implemented security. A corollary of this principle is that data specifications should be as simple as possible, because complex data specifications result in complex validation code. Complex tasks and systems may also need to be guarded by complex security checks, so simple systems should be preferred.

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-637 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-637, Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism'), 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 Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism') during Architecture and Design

MITRE associates mitigation with Architecture and Design; recorded impacts include Other; observed examples include CVE-2007-6067, CVE-2007-1552, and CVE-2007-6479. Use these source-defined anchors to turn CWE-637 into implementation, review, and verification checks for the affected component.

CWE-637: Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism') — MITRE CWE

Triage CWE-637 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-637, Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism'), 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-637

Apply MITRE's full root-cause mapping guidance when using CWE-637, Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism'). 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-637 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-637, Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism'). 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-637: Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')?+

CWE-637: Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism') is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product uses a more complex mechanism than necessary, which could lead to resultant weaknesses when the mechanism is not correctly understood, modeled, configured, implemented, or used. Security mechanisms should be as simple as possible. Complex security mechanisms may engender partial implementations and compatibility problems, with resulting mismatches in assumptions and implemented security. A corollary of this principle is that data specifications should be as simple as possible, because complex data specifications result in complex validation code. Complex tasks and systems may also need to be guarded by complex security checks, so simple systems should be preferred.

What are the security consequences of Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')?+

If exploited, CWE-637 (Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')) it can compromise Other, leading to outcomes such as Other.

How do you prevent or mitigate Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')?+

Recommended mitigations for CWE-637 include: Avoid complex security mechanisms when simpler ones would meet requirements. Avoid complex data models, and unnecessarily complex operations. Adopt architectures that provide guarantees, simplify understanding through elegance and abstraction, and that can be implemented similarly. Modularize, isolate and do not trust complex code, and apply other secure programming principles on these modules (e.g., least privilege) to mitigate vulnerabilities.

Which programming languages are affected by Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')?+

CWE-637 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 Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')?+

MITRE documents real CVEs mapped to CWE-637, including CVE-2007-6067, CVE-2007-1552, CVE-2007-6479 and CVE-2005-2148. 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-637 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-637: Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')

Extended Description

Technical Details

Applicable To

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Impact

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Description

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Code Examples & CVEs

Observed CVE Examples (4)

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