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CWE-234 Variant Incomplete
Failure to Handle Missing Parameter
This vulnerability occurs when a function or method receives fewer arguments than it expects. The function will still attempt to process its expected number of parameters, which can lead to reading…
Definition
What is CWE-234?
This vulnerability occurs when a function or method receives fewer arguments than it expects. The function will still attempt to process its expected number of parameters, which can lead to reading undefined, stale, or arbitrary values from the program's memory or stack, causing crashes or unexpected behavior.
At its core, this flaw is about mismatched expectations between a function's definition and its actual usage. When a caller provides insufficient arguments, the function doesn't receive the data it was designed to process. Instead, it pulls whatever values happen to be in the memory locations (like the stack) where it expected to find its parameters. These values could be remnants from previous operations, uninitialized memory, or even parts of other data structures, leading directly to instability, incorrect calculations, or security breaches.
To prevent this, developers must implement robust input validation at the function's entry point. This includes explicitly checking the number of received arguments, defining safe default values for optional parameters, and using modern language features like default arguments or variadic function safeguards. For lower-level code or APIs, clear documentation and runtime assertions are critical to ensure callers and functions agree on the required contract, preventing the program from operating on garbage data.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-234
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Server earlier allows remote attackers to cause a denial of service (crash) via an HTTP request with a sequence of "%" characters and a missing Host field.
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Chat client allows remote malicious IRC servers to cause a denial of service (crash) via a PART message with (1) a missing channel or (2) a channel that the user is not in.
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Proxy allows remote attackers to cause a denial of service (crash) via an HTTP request to helpout.exe with a missing HTTP version numbers.
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Web server allows disclosure of CGI source code via an HTTP request without the version number.
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Application server allows a remote attacker to read the source code to arbitrary 'jsp' files via a malformed URL request which does not end with an HTTP protocol specification.
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Chat software allows remote attackers to cause a denial of service via malformed GIF89a headers that do not contain a GCT (Global Color Table) or an LCT (Local Color Table) after an Image Descriptor.
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Server allows remote attackers to cause a denial of service (crash) via an HTTP GET request without a URI.
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CGI crashes when called without any arguments.
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 C
The following example demonstrates the weakness.
foo_funct(one, two);
void foo_funct(int one, int two, int three) {
printf("1) %d\n2) %d\n3) %d\n", one, two, three);
} 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-234
- Build and Compilation This issue can be simply combated with the use of proper build process.
- Implementation Forward declare all functions. This is the recommended solution. Properly forward declaration of all used functions will result in a compiler error if too few arguments are sent to a function.
Erkennungssignale
How to detect CWE-234
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-234
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-234?
Wie gravierend ist CWE-234?
Welche Sprachen oder Plattformen sind von CWE-234 betroffen?
Wie kann ich CWE-234 verhindern?
Wie erkennt und behebt Plexicus CWE-234?
Wo erfahre ich mehr über CWE-234?
Frequently asked questions
Was ist CWE-234?
This vulnerability occurs when a function or method receives fewer arguments than it expects. The function will still attempt to process its expected number of parameters, which can lead to reading undefined, stale, or arbitrary values from the program's memory or stack, causing crashes or unexpected behavior.
Wie gravierend ist CWE-234?
MITRE stuft die Exploit-Wahrscheinlichkeit als hoch ein — diese Schwachstelle wird aktiv in freier Wildbahn ausgenutzt und sollte priorisiert behoben werden.
Welche Sprachen oder Plattformen sind von CWE-234 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-234 verhindern?
This issue can be simply combated with the use of proper build process. Forward declare all functions. This is the recommended solution. Properly forward declaration of all used functions will result in a compiler error if too few arguments are sent to a function.
Wie erkennt und behebt Plexicus CWE-234?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-234 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-234?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/234.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-234
CWE-233 Parent
Improper Handling of Parameters
This vulnerability occurs when software fails to correctly process input that contains an unexpected number of parameters, missing fields,…
CWE-235 Sibling
Improper Handling of Extra Parameters
This vulnerability occurs when a system fails to properly manage situations where it receives more parameters, fields, or arguments with…
CWE-236 Sibling
Improper Handling of Undefined Parameters
This vulnerability occurs when software fails to properly manage input parameters, field names, or arguments that it doesn't recognize or…
Ressourcen
Further reading
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.