Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.
CWE-663 Base Draft
Use of a Non-reentrant Function in a Concurrent Context
This vulnerability occurs when a program uses a function that is not safe for reentrancy within a concurrent environment, such as multi-threaded code or signal handlers. If another thread or signal…
Definition
What is CWE-663?
This vulnerability occurs when a program uses a function that is not safe for reentrancy within a concurrent environment, such as multi-threaded code or signal handlers. If another thread or signal handler interrupts and calls the same function, it can corrupt shared data, cause crashes, or create unpredictable behavior.
Non-reentrant functions rely on or modify shared global or static data, making them unsafe when multiple execution flows can interrupt each other. In a concurrent context—like a multi-threaded application or a program using signal handlers—if one thread is inside such a function and another thread or signal handler calls the same function, the shared state can be corrupted. This leads to race conditions, memory corruption, or incorrect program outputs, often manifesting as intermittent, hard-to-debug failures.
To prevent this, developers should identify functions not designed for concurrency (like many traditional C library functions) and protect their use with proper synchronization mechanisms, such as mutexes or semaphores. Alternatively, replace them with thread-safe, reentrant equivalents (often denoted with '_r' suffixes in C). Always audit code for global/static variable usage within functions that may be accessed by multiple threads or signal handlers, and design concurrent systems with clear ownership of shared resources.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-663
-
unsafe calls to library functions from signal handler
-
SIGCHLD signal to FTP server can cause crash under heavy load while executing non-reentrant functions like malloc/free.
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 this example, a signal handler uses syslog() to log a message:
char *message;
void sh(int dummy) {
syslog(LOG_NOTICE,"%s\n",message);
sleep(10);
exit(0);
}
int main(int argc,char* argv[]) {
...
signal(SIGHUP,sh);
signal(SIGTERM,sh);
sleep(10);
exit(0);
}
If the execution of the first call to the signal handler is suspended after invoking syslog(), and the signal handler is called a second time, the memory allocated by syslog() enters an undefined, and possibly, exploitable state. 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-663
- Implementation Use reentrant functions if available.
- Implementation Add synchronization to your non-reentrant function.
- Implementation In Java, use the ReentrantLock Class.
Erkennungssignale
How to detect CWE-663
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-663
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-663?
Wie gravierend ist CWE-663?
Welche Sprachen oder Plattformen sind von CWE-663 betroffen?
Wie kann ich CWE-663 verhindern?
Wie erkennt und behebt Plexicus CWE-663?
Wo erfahre ich mehr über CWE-663?
Frequently asked questions
Was ist CWE-663?
This vulnerability occurs when a program uses a function that is not safe for reentrancy within a concurrent environment, such as multi-threaded code or signal handlers. If another thread or signal handler interrupts and calls the same function, it can corrupt shared data, cause crashes, or create unpredictable behavior.
Wie gravierend ist CWE-663?
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-663 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-663 verhindern?
Use reentrant functions if available. Add synchronization to your non-reentrant function.
Wie erkennt und behebt Plexicus CWE-663?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-663 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-663?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/663.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-663
CWE-662 Parent
Improper Synchronization
This vulnerability occurs when a multi-threaded or multi-process application allows shared resources to be accessed by multiple threads or…
CWE-1058 Sibling
Invokable Control Element in Multi-Thread Context with non-Final Static Storable or Member Element
This happens when a method or function, designed to run in a multi-threaded environment, accesses or modifies a non-final static variable…
CWE-1096 Sibling
Singleton Class Instance Creation without Proper Locking or Synchronization
This flaw occurs when a Singleton class is implemented without proper thread-safe controls, allowing multiple instances to be created in…
CWE-366 Sibling
Race Condition within a Thread
This vulnerability occurs when two or more threads within the same application access and manipulate a shared resource (like a variable,…
CWE-543 Sibling
Use of Singleton Pattern Without Synchronization in a Multithreaded Context
This vulnerability occurs when a singleton pattern is implemented in a multithreaded application without proper synchronization,…
CWE-567 Sibling
Unsynchronized Access to Shared Data in a Multithreaded Context
This vulnerability occurs when multiple threads in an application can read and modify shared data, like static variables, without proper…
CWE-667 Sibling
Improper Locking
This vulnerability occurs when a program fails to correctly acquire or release a lock on a shared resource, such as a file, database…
CWE-764 Sibling
Multiple Locks of a Critical Resource
This vulnerability occurs when a critical resource, such as a file, data structure, or connection, is locked more times than the software…
CWE-820 Sibling
Missing Synchronization
This vulnerability occurs when multiple parts of your application (like threads or processes) use the same resource—such as a variable,…
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.