Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.
CWE-636 Class Draft
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 safer alternative. Examples include reverting to the weakest…
Definition
What is CWE-636?
This vulnerability occurs when a system, upon encountering an error or failure, defaults to its least secure configuration instead of a safer alternative. Examples include reverting to the weakest encryption or the most permissive access rules.
Failing open creates a dangerous gap where the system operates with known, weaker security controls. This directly introduces the vulnerabilities associated with that permissive state, making it significantly easier for an attacker to exploit the system. Often, this design choice is made to prioritize uptime and reduce support overhead, mistakenly valuing continuous functionality over security.
This approach fundamentally undermines security posture and provides administrators with a false sense of protection. The secure alternative is to "fail closed" or "fail safe," where the system denies access or stops operations until the issue can be safely resolved, ensuring security is never automatically compromised for convenience.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-636
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The failure of connection attempts in a web browser resets DNS pin restrictions. An attacker can then bypass the same origin policy by rebinding a domain name to a different IP address. This was an attempt to "fail functional."
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Incorrect prioritization leads to the selection of a weaker cipher. Although it is not known whether this issue occurred in implementation or design, it is feasible that a poorly designed algorithm could be a factor.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
Identifiziere einen Codepfad, der nicht vertrauenswürdige Eingaben ohne Validierung verarbeitet.
- 2
Erzeuge eine Payload, die das unsichere Verhalten auslöst — Injection, Traversal, Overflow oder Logik-Missbrauch.
- 3
Liefere die Payload über einen normalen Request aus und beobachte die Reaktion der Anwendung.
- 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.
// 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
// 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-636
- Architecture and Design Subdivide and allocate resources and components so that a failure in one part does not affect the entire product.
Erkennungssignale
How to detect CWE-636
Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.
Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.
Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.
CWE-636
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Häufig gestellte Fragen Was ist CWE-636?
Wie gravierend ist CWE-636?
Welche Sprachen oder Plattformen sind von CWE-636 betroffen?
Wie kann ich CWE-636 verhindern?
Wie erkennt und behebt Plexicus CWE-636?
Wo erfahre ich mehr über CWE-636?
Frequently asked questions
Was ist CWE-636?
This vulnerability occurs when a system, upon encountering an error or failure, defaults to its least secure configuration instead of a safer alternative. Examples include reverting to the weakest encryption or the most permissive access rules.
Wie gravierend ist CWE-636?
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-636 betroffen?
MITRE lists the following affected platforms: Not Technology-Specific, ICS/OT.
Wie kann ich CWE-636 verhindern?
Subdivide and allocate resources and components so that a failure in one part does not affect the entire product.
Wie erkennt und behebt Plexicus CWE-636?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-636 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-636?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/636.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-636
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-637 Sibling
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…
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
- MITRE — offizielle CWE-636 https://cwe.mitre.org/data/definitions/636.html
- The Protection of Information in Computer Systems http://web.mit.edu/Saltzer/www/publications/protection/
- Failing Securely https://web.archive.org/web/20221017053210/https://www.cisa.gov/uscert/bsi/articles/knowledge/principles/failing-securely
Bereit, das Wesentliche zu validieren?
Bereit zu validieren, was zählt.
Plexicus ist Proof-Driven AppSec: validierte Funde, kontextuelles Verständnis und geprüfte Remediation — in Evidenz verankert, mit Ihnen gescoped.