CWE-637 Class Draft

Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')

This weakness occurs when a security feature is implemented with excessive complexity, creating unnecessary risk. Overly intricate protection mechanisms are harder to understand, configure, and…

Definition

What is CWE-637?

This weakness occurs when a security feature is implemented with excessive complexity, creating unnecessary risk. Overly intricate protection mechanisms are harder to understand, configure, and implement correctly, often leading to security gaps and misconfigurations.
Security controls should follow the principle of 'economy of mechanism'—the simpler they are, the more reliable they become. Complex designs increase the chance of implementation errors, compatibility issues, and mismatches between the intended security model and its real-world deployment. Developers are more likely to correctly implement, test, and maintain straightforward solutions. This principle also applies to data structures and validation logic. Overly complex data specifications force you to write equally complex validation code, which is prone to bugs. Whenever possible, favor simple system architectures and data models, as they naturally require simpler and more robust security checks.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-637

  • CVE-2007-6067

    Support for complex regular expressions leads to a resultant algorithmic complexity weakness (CWE-407).

  • CVE-2007-1552

    Either 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).

  • CVE-2007-6479

    In 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.

  • CVE-2005-2148

    The 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.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    Identifiziere einen Codepfad, der nicht vertrauenswürdige Eingaben ohne Validierung verarbeitet.

  2. 2

    Erzeuge eine Payload, die das unsichere Verhalten auslöst — Injection, Traversal, Overflow oder Logik-Missbrauch.

  3. 3

    Liefere die Payload über einen normalen Request aus und beobachte die Reaktion der Anwendung.

  4. 4

    Iteriere, bis die Antwort Daten preisgibt, Angreifer-Code ausführt oder Berechtigungen eskaliert.

Verwundbares Codebeispiel

Vulnerable pseudo

MITRE hat kein Codebeispiel für diese CWE veröffentlicht. Das untenstehende Muster ist illustrativ — kanonische Referenzen findest du unter Ressourcen.

Verwundbar pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
Sicheres Codebeispiel

Secure pseudo

Sicher pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste

How to prevent CWE-637

  • Architecture and Design 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.
Erkennungssignale

How to detect CWE-637

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-637 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen
Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-637?

This weakness occurs when a security feature is implemented with excessive complexity, creating unnecessary risk. Overly intricate protection mechanisms are harder to understand, configure, and implement correctly, often leading to security gaps and misconfigurations.

Wie gravierend ist CWE-637?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-637 betroffen?

MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.

Wie kann ich CWE-637 verhindern?

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.

Wie erkennt und behebt Plexicus CWE-637?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-637 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-637?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/637.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-637

CWE-657 Parent

Violation of Secure Design Principles

This weakness occurs when a system's architecture or design fails to follow fundamental security principles, creating a flawed foundation…

CWE-1192 Sibling

Improper Identifier for IP Block used in System-On-Chip (SOC)

This weakness occurs when a System-on-Chip (SoC) lacks a secure, unique, and permanent identifier for its internal hardware components (IP…

CWE-1395 Sibling

Dependency on Vulnerable Third-Party Component

This vulnerability occurs when your software relies on an external library, framework, or module that contains known security flaws.

CWE-250 Sibling

Execution with Unnecessary Privileges

This vulnerability occurs when software runs with higher permissions than it actually needs to perform its tasks. This excessive privilege…

CWE-636 Sibling

Not Failing Securely ('Failing Open')

This vulnerability occurs when a system, upon encountering an error or failure, defaults to its least secure configuration instead of a…

CWE-638 Sibling

Not Using Complete Mediation

This vulnerability occurs when software fails to verify access permissions every single time a user or process tries to use a resource.…

CWE-653 Sibling

Improper Isolation or Compartmentalization

This vulnerability occurs when an application fails to enforce strong boundaries between components that operate at different security…

CWE-654 Sibling

Reliance on a Single Factor in a Security Decision

This vulnerability occurs when a system's security check depends almost entirely on just one condition, object, or piece of data to decide…

CWE-655 Sibling

Insufficient Psychological Acceptability

This weakness occurs when security features are so cumbersome or confusing that well-intentioned users feel forced to turn them off or…

Ressourcen

Further reading

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