Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.
CWE-240 Base Draft
Improper Handling of Inconsistent Structural Elements
This vulnerability occurs when a system fails to properly manage situations where related data structures or elements should match but are inconsistent.
Definition
What is CWE-240?
This vulnerability occurs when a system fails to properly manage situations where related data structures or elements should match but are inconsistent.
This weakness stems from a lack of validation or reconciliation logic when processing interconnected data points. For example, an application might check a user's role in one part of a request but ignore a conflicting permission flag sent in another, or it might parse a file header but not verify that the declared data length matches the actual payload size. Without proper handling, these inconsistencies can be exploited to bypass security checks, corrupt data, or cause unexpected system behavior.
To prevent this, developers should implement strict consistency checks wherever structural relationships exist. This includes validating that all linked elements (like headers and bodies, metadata and content, or multi-part transaction states) are synchronized and logically coherent before processing. Defensive coding practices, such as using immutable data structures after validation or adopting a single source of truth for critical attributes, can effectively eliminate the risks posed by inconsistent elements.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-240
-
Chain: "Heartbleed" bug receives an inconsistent length parameter (CWE-130) enabling an out-of-bounds read (CWE-126), returning memory that could include private cryptographic keys and other sensitive data.
-
Web application firewall consumes excessive memory when an HTTP request contains a large Content-Length value but no POST data.
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
In the following C/C++ example the method processMessageFromSocket() will get a message from a socket, placed into a buffer, and will parse the contents of the buffer into a structure that contains the message length and the message body. A for loop is used to copy the message body into a local character string which will be passed to another method for processing.
int processMessageFromSocket(int socket) {
int success;
char buffer[BUFFER_SIZE];
char message[MESSAGE_SIZE];
```
// get message from socket and store into buffer*
*//Ignoring possibliity that buffer > BUFFER_SIZE*
if (getMessage(socket, buffer, BUFFER_SIZE) > 0) {
```
```
// place contents of the buffer into message structure*
ExMessage *msg = recastBuffer(buffer);
*// copy message body into string for processing*
int index;
for (index = 0; index < msg->msgLength; index++) {
```
message[index] = msg->msgBody[index];
}
message[index] = '\0';
```
// process message*
success = processMessage(message);}
return success;} 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-240
- Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
- Implementation Validate input at trust boundaries; use allowlists, not denylists.
- Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
- Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
- Operation Monitor logs for the runtime signals listed in the next section.
Erkennungssignale
How to detect CWE-240
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-240
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-240?
Wie gravierend ist CWE-240?
Welche Sprachen oder Plattformen sind von CWE-240 betroffen?
Wie kann ich CWE-240 verhindern?
Wie erkennt und behebt Plexicus CWE-240?
Wo erfahre ich mehr über CWE-240?
Frequently asked questions
Was ist CWE-240?
This vulnerability occurs when a system fails to properly manage situations where related data structures or elements should match but are inconsistent.
Wie gravierend ist CWE-240?
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-240 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-240 verhindern?
Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.
Wie erkennt und behebt Plexicus CWE-240?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-240 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-240?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/240.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-240
CWE-237 Parent
Improper Handling of Structural Elements
This vulnerability occurs when an application fails to properly validate, sanitize, or interpret the complex internal parts of structured…
CWE-238 Sibling
Improper Handling of Incomplete Structural Elements
This vulnerability occurs when software fails to properly process or validate data structures that are missing required components or are…
CWE-239 Sibling
Failure to Handle Incomplete Element
This vulnerability occurs when a system fails to properly manage or validate data elements that are missing required parts or are only…
CWE-130 Child
Improper Handling of Length Parameter Inconsistency
This vulnerability occurs when a program reads a structured data packet or message but fails to properly validate that the declared length…
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.