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-758 Class Incomplete
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
This weakness occurs when software depends on specific behaviors of an API, data structure, or system component that are not formally guaranteed by its specification. The code assumes these…
Definition
What is CWE-758?
This weakness occurs when software depends on specific behaviors of an API, data structure, or system component that are not formally guaranteed by its specification. The code assumes these behaviors will always work a certain way, but they might change or fail under different conditions.
Relying on undefined or platform-specific behavior creates fragile code that can break unexpectedly. For example, a function might return results in a particular order on your development machine, but a different compiler or operating system version could alter that order, causing logic errors or crashes.
This often surfaces during porting to a new environment or during complex interactions between components. To avoid this, developers should strictly use documented, standardized behaviors and avoid assumptions about internal implementation details that aren't part of the official contract.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-758
-
Change in C compiler behavior causes resultant buffer overflows in programs that depend on behaviors that were undefined in the C standard.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
This code assumes a particular function will always be found at a particular address. It assigns a pointer to that address and calls the function.
- 2
The same function may not always be found at the same memory address. This could lead to a crash, or an attacker may alter the memory at the expected address, leading to arbitrary code execution.
- 3
The following function returns a stack address.
Verwundbares Codebeispiel
Vulnerable C
This code assumes a particular function will always be found at a particular address. It assigns a pointer to that address and calls the function.
int (*pt2Function) (float, char, char)=0x08040000;
int result2 = (*pt2Function) (12, 'a', 'b');
```
// Here we can inject code to execute.* 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-758
- 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-758
CWE-758
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-758?
Wie gravierend ist CWE-758?
Welche Sprachen oder Plattformen sind von CWE-758 betroffen?
Wie kann ich CWE-758 verhindern?
Wie erkennt und behebt Plexicus CWE-758?
Wo erfahre ich mehr über CWE-758?
Frequently asked questions
Was ist CWE-758?
This weakness occurs when software depends on specific behaviors of an API, data structure, or system component that are not formally guaranteed by its specification. The code assumes these behaviors will always work a certain way, but they might change or fail under different conditions.
Wie gravierend ist CWE-758?
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-758 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-758 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-758?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-758 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-758?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/758.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-758
CWE-710 Parent
Improper Adherence to Coding Standards
This weakness occurs when developers don't consistently follow established coding standards and best practices, which can introduce…
CWE-1041 Sibling
Use of Redundant Code
This weakness occurs when a codebase contains identical or nearly identical logic duplicated across multiple functions, methods, or…
CWE-1044 Sibling
Architecture with Number of Horizontal Layers Outside of Expected Range
This occurs when a software system is built with either too many or too few distinct architectural layers, falling outside a recommended…
CWE-1048 Sibling
Invokable Control Element with Large Number of Outward Calls
This weakness occurs when a single function, method, or callable code block makes an excessively high number of calls to other objects or…
CWE-1059 Sibling
Insufficient Technical Documentation
This weakness occurs when a software or hardware product lacks comprehensive technical documentation. Missing or incomplete details about…
CWE-1061 Sibling
Insufficient Encapsulation
This weakness occurs when a software component exposes too much of its internal workings, such as data structures or implementation logic.…
CWE-1065 Sibling
Runtime Resource Management Control Element in a Component Built to Run on Application Servers
This weakness occurs when an application built to run on a managed application server bypasses the server's high-level APIs and instead…
CWE-1066 Sibling
Missing Serialization Control Element
This weakness occurs when a class or data structure is marked as serializable but lacks the required control methods to properly handle…
CWE-1068 Sibling
Inconsistency Between Implementation and Documented Design
This weakness occurs when the actual code implementation deviates from the intended design described in its official documentation,…
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.