CWE-271 Clase Incompleto High likelihood

Privilege Dropping / Lowering Errors

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.

Definición

What is CWE-271?

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.
In secure software design, a common practice is for a high-privilege process to perform a sensitive operation and then immediately lower its permissions before interacting with lower-privileged entities. This flaw breaks that chain of trust. When a system hands off a file, process, or network connection without first dropping these elevated rights, it effectively grants those high-level permissions to the receiving party, which may not be authorized to have them. This creates a dangerous privilege escalation path. By failing to contain permissions within their intended scope, the flaw allows excessive access to spread throughout the application environment. An attacker who gains control of the lower-privileged component can then inherit and abuse these unintended permissions, potentially taking full control of the system or accessing restricted data.
Impacto en el mundo real

Real-world CVEs caused by CWE-271

  • CVE-2000-1213

    Program does not drop privileges after acquiring the raw socket.

  • CVE-2001-0559

    Setuid program does not drop privileges after a parsing error occurs, then calls another program to handle the error.

  • CVE-2001-0787

    Does not drop privileges in related groups when lowering privileges.

  • CVE-2002-0080

    Does not drop privileges in related groups when lowering privileges.

  • CVE-2001-1029

    Does not drop privileges before determining access to certain files.

  • CVE-1999-0813

    Finger daemon does not drop privileges when executing programs on behalf of the user being fingered.

  • CVE-1999-1326

    FTP server does not drop privileges if a connection is aborted during file transfer.

  • CVE-2000-0172

    Program only uses seteuid to drop privileges.

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    Identifica una ruta de código que maneje entrada no confiable sin validación.

  2. 2

    Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.

  3. 3

    Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.

  4. 4

    Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.

Ejemplo de código vulnerable

Vulnerable C

The following code calls chroot() to restrict the application to a subset of the filesystem below APP_HOME in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.

Vulnerable C 
chroot(APP_HOME);
  chdir("/");
  FILE* data = fopen(argv[1], "r+");
  ...
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-271

  • Architecture and Design Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
  • Architecture and Design / Operation Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
  • Architecture and Design Consider following the principle of separation of privilege. Require multiple conditions to be met before permitting access to a system resource.
Señales de detección

How to detect CWE-271

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.

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-271 y abre un PR de corrección en menos de 60 segundos.

Codex Remedium escanea cada commit, identifica esta debilidad concreta y entrega un pull request listo para revisión con el parche. Sin tickets. Sin traspasos.

Solicitar demo Probar Plexicus gratis
Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-271?

This vulnerability occurs when a system or process fails to reduce its elevated permissions before transferring control of a resource to a less-privileged user or component.

¿Qué gravedad tiene CWE-271?

MITRE califica la probabilidad de explotación como Alta — esta debilidad se explota activamente en la práctica y debe priorizarse para su remediación.

¿Qué lenguajes o plataformas se ven afectados por CWE-271?

MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.

¿Cómo puedo prevenir CWE-271?

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to…

¿Cómo detecta y corrige Plexicus CWE-271?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-271 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-271?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/271.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-271

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CWE-250 Hermano

Execution with Unnecessary Privileges

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CWE-266 Hermano

Incorrect Privilege Assignment

This vulnerability occurs when a system mistakenly grants a user, process, or entity a specific permission or privilege they should not…

CWE-267 Hermano

Privilege Defined With Unsafe Actions

This vulnerability occurs when a system grants a user, role, or process a specific permission that can be misused to perform dangerous,…

CWE-268 Hermano

Privilege Chaining

Privilege chaining occurs when an attacker combines two separate permissions or capabilities, neither of which is dangerous on its own, to…

CWE-270 Hermano

Privilege Context Switching Error

This vulnerability occurs when an application fails to properly manage user permissions while moving between different security contexts,…

CWE-274 Hermano

Improper Handling of Insufficient Privileges

This vulnerability occurs when an application fails to properly manage situations where it lacks the necessary permissions to execute an…

CWE-648 Hermano

Incorrect Use of Privileged APIs

This vulnerability occurs when software incorrectly uses functions that require special permissions. Attackers can exploit these mistakes…

CWE-272 Hijo

Least Privilege Violation

This vulnerability occurs when software fails to reduce its elevated system privileges after completing a sensitive operation, leaving it…

Recursos

Further reading

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