Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
CWE-393 Base Draft
Return of Wrong Status Code
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in…
Definition
What is CWE-393?
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in unexpected and potentially insecure ways.
When a system relies on these incorrect return codes to make decisions, it can lead to unpredictable application states, logic errors, and instability. For example, a function might incorrectly report a successful file deletion or a failed authentication check, causing the program flow to proceed down the wrong path.
If these status checks are part of security-critical logic—like access control, authentication, or data validation—the consequences are severe. The application might grant access to unauthorized users, assume a dangerous operation succeeded safely, or fail to alert on genuine security failures, creating hidden vulnerabilities that attackers can exploit.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-393
-
DNS server returns wrong response code for non-existent AAAA record, which effectively says that the domain is inaccessible.
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Hardware-specific implementation of system call causes incorrect results from geteuid.
-
Chain: System call returns wrong value (CWE-393), leading to a resultant NULL dereference (CWE-476).
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chain: incorrect "goto" in Apple SSL product bypasses certificate validation, allowing Adversary-in-the-Middle (AITM) attack (Apple "goto fail" bug). CWE-705 (Incorrect Control Flow Scoping) -> CWE-561 (Dead Code) -> CWE-295 (Improper Certificate Validation) -> CWE-393 (Return of Wrong Status Code) -> CWE-300 (Channel Accessible by Non-Endpoint).
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 Java
In the following example, an HTTP 404 status code is returned in the event of an IOException encountered in a Java servlet. A 404 code is typically meant to indicate a non-existent resource and would be somewhat misleading in this case.
try {
```
// something that might throw IOException*
...} catch (IOException ioe) {
```
response.sendError(SC_NOT_FOUND);
} 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-393
- 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-393
Plexicus erkennt CWE-393 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.
Häufig gestellte Fragen Was ist CWE-393?
Wie gravierend ist CWE-393?
Welche Sprachen oder Plattformen sind von CWE-393 betroffen?
Wie kann ich CWE-393 verhindern?
Wie erkennt und behebt Plexicus CWE-393?
Wo erfahre ich mehr über CWE-393?
Frequently asked questions
Was ist CWE-393?
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in unexpected and potentially insecure ways.
Wie gravierend ist CWE-393?
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-393 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-393 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-393?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-393 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-393?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/393.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-393
CWE-684 Parent
Incorrect Provision of Specified Functionality
This weakness occurs when software behaves differently than its documented specifications, which can mislead users and create security…
CWE-1245 Sibling
Improper Finite State Machines (FSMs) in Hardware Logic
This vulnerability occurs when hardware logic contains flawed Finite State Machines (FSMs). Attackers can exploit these design errors to…
CWE-392 Sibling
Missing Report of Error Condition
This vulnerability occurs when a system fails to properly signal that an error has happened. Instead of returning a clear error code,…
CWE-440 Sibling
Expected Behavior Violation
This weakness occurs when a software component, such as a function, API, or feature, fails to act as documented or intended. The system's…
CWE-446 Sibling
UI Discrepancy for Security Feature
This vulnerability occurs when a user interface incorrectly displays a security feature as active or properly configured, misleading users…
CWE-451 Sibling
User Interface (UI) Misrepresentation of Critical Information
This vulnerability occurs when a user interface fails to accurately display or highlight crucial information, potentially misleading users…
CWE-912 Sibling
Hidden Functionality
Hidden functionality refers to undocumented features, commands, or code within a product that are not part of its official specification…
Ressourcen
Further reading
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