CWE-911 Base Incompleto Medium likelihood

Improper Update of Reference Count

This vulnerability occurs when a program uses a reference counter to track resource usage but fails to update the count correctly, either by missing an update or applying an incorrect value.

Definición

What is CWE-911?

This vulnerability occurs when a program uses a reference counter to track resource usage but fails to update the count correctly, either by missing an update or applying an incorrect value.

Reference counting is a common technique for managing resources like memory blocks or file handles. The system tracks how many active pointers or handles refer to a resource, and the resource is only freed when this count drops to zero. If the count is accidentally decremented too early, the resource can be prematurely released while still in use, leading to crashes or use-after-free errors. Conversely, if the reference count isn't decremented when a reference is removed, the count never reaches zero. This creates a resource leak, where unused memory or handles are never reclaimed. Over time, these leaks degrade performance and can exhaust system resources, causing instability or denial of service.

Impacto en el mundo real

Real-world CVEs caused by CWE-911

CVE-2002-0574

chain: reference count is not decremented, leading to memory leak in OS by sending ICMP packets.
CVE-2004-0114

Reference count for shared memory not decremented when a function fails, potentially allowing unprivileged users to read kernel memory.
CVE-2006-3741

chain: improper reference count tracking leads to file descriptor consumption
CVE-2007-1383

chain: integer overflow in reference counter causes the same variable to be destroyed twice.
CVE-2007-1700

Incorrect reference count calculation leads to improper object destruction and code execution.
CVE-2008-2136

chain: incorrect update of reference count leads to memory leak.
CVE-2008-2785

chain/composite: use of incorrect data type for a reference counter allows an overflow of the counter, leading to a free of memory that is still in use.
CVE-2008-5410

Improper reference counting leads to failure of cryptographic operations.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

1
Identifica una ruta de código que maneje entrada no confiable sin validación.
2
Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.
3
Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.
4
Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.

Ejemplo de código vulnerable

Vulnerable pseudo

MITRE no ha publicado un ejemplo de código para esta CWE. El patrón siguiente es ilustrativo — consulta Recursos para referencias canónicas.

Vulnerable pseudo

// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}

Ejemplo de código seguro

Secure pseudo

Seguro 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-911

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-911

SAST High

Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.

DAST Moderate

Ejecuta pruebas dinámicas de seguridad de aplicaciones (DAST) contra el endpoint en vivo.

Runtime Moderate

Vigila los logs en tiempo de ejecución para detectar trazas de excepción inusuales, entradas malformadas o intentos de bypass de autorización.

Code review Moderate

Revisión de código: marca cualquier código nuevo que maneje entrada desde esta superficie sin usar los helpers validados del framework.

CWE-911

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.

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-911?

This vulnerability occurs when a program uses a reference counter to track resource usage but fails to update the count correctly, either by missing an update or applying an incorrect value.

¿Qué gravedad tiene CWE-911?

MITRE califica la probabilidad de explotación como Media — la explotación es realista pero suele requerir condiciones específicas.

¿Qué lenguajes o plataformas se ven afectados por CWE-911?

MITRE lists the following affected platforms: C, C++.

¿Cómo puedo prevenir CWE-911?

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-911?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-911 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-911?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/911.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-911

CWE-664 Padre

Listo para validar lo que importa.

Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.

Reservar Pentest

Improper Update of Reference Count

What is CWE-911?

Real-world CVEs caused by CWE-911

Ruta del atacante paso a paso

Vulnerable pseudo

Secure pseudo

How to prevent CWE-911

How to detect CWE-911

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-911

Improper Control of a Resource Through its Lifetime

Incorrect Access of Indexable Resource ('Range Error')

Creation of Emergent Resource

Improper Preservation of Consistency Between Independent Representations of Shared State

Reliance on Component That is Not Updateable

Information Loss or Omission

Incomplete Internal State Distinction

Uncontrolled Resource Consumption

Improper Resource Shutdown or Release

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`