CWE-637: Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')
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.
View on MITREExtended 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.
Technical Details
- Structure
- Simple
Applicable To
Security Consequences
Scope
Impact
Mitigation Strategies
Phase
Description
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.
Detection Methods
No detection method information available for this CWE.
Code Examples & CVEs
Observed CVE Examples (4)
Support for complex regular expressions leads to a resultant algorithmic complexity weakness (CWE-407).
View DetailsEither a filename extension and a Content-Type header could be used to infer the file type, but the developer only checks the Content-Type, enabling unrestricted file upload (CWE-434).
View DetailsIn Apache environments, a "filename.php.gif" can be redirected to the PHP interpreter instead of being sent as an image/gif directly to the user. Not knowing this, the developer only checks the last extension of a submitted filename, enabling arbitrary code execution.
View DetailsThe developer cleanses the $_REQUEST superglobal array, but PHP also populates $_GET, allowing attackers to bypass the protection mechanism and conduct SQL injection attacks against code that uses $_GET.
View DetailsCWE Relationships
No relationship information available for this 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.