Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.
CWE-831 Variante Incompleto
Signal Handler Function Associated with Multiple Signals
This vulnerability occurs when a single function is registered to handle multiple different operating system signals, creating potential race conditions if that function isn't carefully designed.
Definición
What is CWE-831?
This vulnerability occurs when a single function is registered to handle multiple different operating system signals, creating potential race conditions if that function isn't carefully designed.
When the same function handles multiple signals, an attacker can exploit timing issues by sending a second signal while the handler is still processing the first. If the handler uses shared resources like global variables or non-reentrant functions, this interruption can corrupt program state, potentially leading to crashes, denial of service, or even code execution.
Even without classic race conditions, this pattern creates risk. Attackers can trigger the handler multiple times by sending different signals sequentially, causing unintended side effects. This is especially dangerous for handlers designed to run only once, as forced re-execution can bypass security controls or destabilize the application.
Impacto en el mundo real
Real-world CVEs caused by CWE-831
Todavía no hay CVEs públicos enlazados a esta CWE en el catálogo de MITRE.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
This code registers the same signal handler function with two different signals.
- 2
This code registers the same signal handler function with two different signals (CWE-831). If those signals are sent to the process, the handler creates a log message (specified in the first argument to the program) and exits.
- 3
The handler function uses global state (globalVar and logMessage), and it can be called by both the SIGHUP and SIGTERM signals. An attack scenario might follow these lines:
- 4
- The program begins execution, initializes logMessage, and registers the signal handlers for SIGHUP and SIGTERM. - The program begins its "normal" functionality, which is simplified as sleep(), but could be any functionality that consumes some time. - The attacker sends SIGHUP, which invokes handler (call this "SIGHUP-handler"). - SIGHUP-handler begins to execute, calling syslog(). - syslog() calls malloc(), which is non-reentrant. malloc() begins to modify metadata to manage the heap. - The attacker then sends SIGTERM. - SIGHUP-handler is interrupted, but syslog's malloc call is still executing and has not finished modifying its metadata. - The SIGTERM handler is invoked. - SIGTERM-handler records the log message using syslog(), then frees the logMessage variable.
- 5
At this point, the state of the heap is uncertain, because malloc is still modifying the metadata for the heap; the metadata might be in an inconsistent state. The SIGTERM-handler call to free() is assuming that the metadata is inconsistent, possibly causing it to write data to the wrong location while managing the heap. The result is memory corruption, which could lead to a crash or even code execution, depending on the circumstances under which the code is running.
Ejemplo de código vulnerable
Vulnerable C
This code registers the same signal handler function with two different signals.
void handler (int sigNum) {
...
}
int main (int argc, char* argv[]) {
signal(SIGUSR1, handler)
signal(SIGUSR2, handler)
} Ejemplo de código seguro
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.
Lista de prevención
How to prevent CWE-831
- 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.
Señales de detección
How to detect CWE-831
Ejecuta pruebas dinámicas de seguridad de aplicaciones (DAST) contra el endpoint en vivo.
Vigila los logs en tiempo de ejecución para detectar trazas de excepción inusuales, entradas malformadas o intentos de bypass de autorización.
Revisión de código: marca cualquier código nuevo que maneje entrada desde esta superficie sin usar los helpers validados del framework.
CWE-831
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.
Preguntas frecuentes ¿Qué es CWE-831?
¿Qué gravedad tiene CWE-831?
¿Qué lenguajes o plataformas se ven afectados por CWE-831?
¿Cómo puedo prevenir CWE-831?
¿Cómo detecta y corrige Plexicus CWE-831?
¿Dónde puedo aprender más sobre CWE-831?
Frequently asked questions
¿Qué es CWE-831?
This vulnerability occurs when a single function is registered to handle multiple different operating system signals, creating potential race conditions if that function isn't carefully designed.
¿Qué gravedad tiene CWE-831?
MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.
¿Qué lenguajes o plataformas se ven afectados por CWE-831?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-831?
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.
¿Cómo detecta y corrige Plexicus CWE-831?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-831 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.
¿Dónde puedo aprender más sobre CWE-831?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/831.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-831
CWE-364 Padre
Signal Handler Race Condition
A signal handler race condition occurs when a program's signal handling routine is vulnerable to timing issues, allowing its state to be…
CWE-432 Hermano
Dangerous Signal Handler not Disabled During Sensitive Operations
This vulnerability occurs when a program's signal handler, which shares resources like global variables with other handlers, can be…
CWE-828 Hermano
Signal Handler with Functionality that is not Asynchronous-Safe
This weakness occurs when a program's signal handler contains code that is not asynchronous-safe. This means the handler can be…
Recursos
Further reading
- MITRE — CWE-831 oficial https://cwe.mitre.org/data/definitions/831.html
- Delivering Signals for Fun and Profit https://lcamtuf.coredump.cx/signals.txt
- Race Condition: Signal Handling https://vulncat.fortify.com/en/detail?id=desc.structural.cpp.race_condition_signal_handling#:~:text=Signal%20handling%20race%20conditions%20can,installed%20to%20handle%20multiple%20signals.s
¿Listo para validar lo que importa?
Listo para validar lo que importa.
Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.