CWE-241 Base Draft

Improper Handling of Unexpected Data Type

This vulnerability occurs when software fails to properly validate or safely process data that arrives in an unexpected format. For example, the system might expect a numeric input but receives text…

Definition

What is CWE-241?

At its core, this weakness is about broken assumptions in your code's data handling. Developers often write logic expecting data in a specific format—like integers, strings, or structured objects. When the incoming data doesn't match that type (e.g., a user submits 'abc' where a number is required), the application may throw unhandled exceptions, behave unpredictably, or expose internal system details through error messages. To prevent this, implement strict input validation and type checking at all system boundaries. Use strong typing in your programming language where possible, and always sanitize and verify data from external sources like user inputs, APIs, or files before processing. Defensive coding practices, such as using try-catch blocks and designing functions to handle a range of input types gracefully, are essential to maintain stability and security when faced with unexpected data.

Auswirkungen in der Praxis

Real-world CVEs caused by CWE-241

CVE-1999-1156

FTP server crash via PORT command with non-numeric character.
CVE-2004-0270

Anti-virus product has assert error when line length is non-numeric.

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.

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-241

Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Implementation Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.

Erkennungssignale

How to detect CWE-241

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.

CWE-241

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.

Request AI Swarm Pentest

Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-241?

Wie gravierend ist CWE-241?

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-241 betroffen?

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

Wie kann ich CWE-241 verhindern?

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and…

Wie erkennt und behebt Plexicus CWE-241?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-241 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-241?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/241.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-241

CWE-228 Parent

Bereit zu validieren, was zählt.

Plexicus ist Proof-Driven AppSec: validierte Funde, kontextuelles Verständnis und geprüfte Remediation — in Evidenz verankert, mit Ihnen gescoped.

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Improper Handling of Unexpected Data Type

What is CWE-241?

Real-world CVEs caused by CWE-241

Angreiferpfad Schritt für Schritt

Vulnerable pseudo

Secure pseudo

How to prevent CWE-241

How to detect CWE-241

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-241

Improper Handling of Syntactically Invalid Structure

Improper Handling of Missing Special Element

Improper Handling of Additional Special Element

Improper Handling of Inconsistent Special Elements

Improper Handling of Values

Improper Handling of Parameters

Improper Handling of Structural Elements

Further reading

Bereit zu validieren, was zählt.

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`