CWE-163 Variante Incompleto

Improper Neutralization of Multiple Trailing Special Elements

This vulnerability occurs when software accepts external input but fails to properly sanitize or incorrectly handles multiple trailing special characters or elements. When this unsanitized data is…

Definición

What is CWE-163?

This vulnerability occurs when software accepts external input but fails to properly sanitize or incorrectly handles multiple trailing special characters or elements. When this unsanitized data is passed to another system component, these elements can be interpreted in harmful, unintended ways.
During data processing, trailing special elements like repeated slashes, dots, or escape sequences can trick parsers or handlers. If an application doesn't clean up these multiple trailing elements, it can cause the downstream component to misinterpret boundaries, change execution paths, or trigger unexpected actions, creating a security flaw. For developers, this means input validation must account for sequences of special characters at the end of data strings, not just single instances. Robust sanitization should collapse or remove illegitimate trailing element repetitions before data is forwarded, preventing manipulation of file paths, command arguments, or protocol directives.
Impacto en el mundo real

Real-world CVEs caused by CWE-163

  • CVE-2002-1078

    Directory listings in web server using multiple trailing slash

  • CVE-2004-0281

    Multiple trailing dot allows directory listing

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 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-163

  • Developers should anticipate that multiple trailing special elements will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
  • Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • Implementation While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).
  • Implementation Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Señales de detección

How to detect CWE-163

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-163 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-163?

This vulnerability occurs when software accepts external input but fails to properly sanitize or incorrectly handles multiple trailing special characters or elements. When this unsanitized data is passed to another system component, these elements can be interpreted in harmful, unintended ways.

¿Qué gravedad tiene CWE-163?

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-163?

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

¿Cómo puedo prevenir CWE-163?

Developers should anticipate that multiple trailing special elements will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system. Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform…

¿Cómo detecta y corrige Plexicus CWE-163?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-163 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-163?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/163.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-163

CWE-162 Padre

Improper Neutralization of Trailing Special Elements

This vulnerability occurs when an application fails to properly sanitize or remove trailing special characters from user-supplied input…

CWE-42 Hermano

Path Equivalence: 'filename.' (Trailing Dot)

This vulnerability occurs when a system accepts file or directory paths that end with a dot (like 'file.txt.' or 'folder.') without…

CWE-46 Hermano

Path Equivalence: 'filename ' (Trailing Space)

This vulnerability occurs when an application processes file paths that end with a space character (like 'document.txt ') without properly…

CWE-49 Hermano

Path Equivalence: 'filename/' (Trailing Slash)

This vulnerability occurs when an application accepts file or directory paths that end with a slash (e.g., 'documents/') without properly…

CWE-54 Hermano

Path Equivalence: 'filedir\' (Trailing Backslash)

This vulnerability occurs when an application accepts file or directory paths that end with a backslash (like 'filedir\') without properly…

CWE-43 Hijo

Path Equivalence: 'filename....' (Multiple Trailing Dot)

This vulnerability occurs when an application accepts file or directory paths containing multiple trailing dots (like 'file....') without…

CWE-52 Hijo

Path Equivalence: '/multiple/trailing/slash//'

This vulnerability occurs when an application accepts file or directory paths containing multiple consecutive forward slashes (like…

Recursos

Further reading

Listo cuando tú lo estés

Deja de pagar por desarrollador.
Empieza a cerrar el bucle.

Plexicus es el ASPM nativo de IA que escanea, filtra, corrige, pentestea y explica — de forma autónoma. Desarrolladores ilimitados, repos ilimitados, acciones de IA de uso justo. Nivel gratuito real, €269/mo anual cuando estés listo.

Comenzar gratis Reservar una demo