CWE-32 Variante Incompleto

Path Traversal: '...' (Triple Dot)

This vulnerability occurs when an application builds file paths using user input but fails to properly filter out '...' (triple dot) sequences. Attackers can exploit this to escape restricted…

Definición

What is CWE-32?

This vulnerability occurs when an application builds file paths using user input but fails to properly filter out '...' (triple dot) sequences. Attackers can exploit this to escape restricted directories and access unauthorized files or folders on the server.
The triple dot sequence ('...') is a clever evasion technique that can bypass basic path traversal filters. On Windows systems, it's often interpreted as '..\..', allowing attackers to jump two directory levels at once. Many security checks only look for the standard double-dot ('..'), making this a simple yet effective way to slip past incomplete validations. This flaw often stems from overly simplistic filtering logic. For example, if a system only removes './' sequences from an input like '....//', the remaining characters can collapse back into a dangerous '..' path traversal payload. Developers need to implement robust path normalization and canonicalization before checking directory boundaries, rather than relying on blacklisting specific character patterns.
Impacto en el mundo real

Real-world CVEs caused by CWE-32

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-32

  • 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. When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434. Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.
  • 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-32

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-32 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.

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-32?

This vulnerability occurs when an application builds file paths using user input but fails to properly filter out '...' (triple dot) sequences. Attackers can exploit this to escape restricted directories and access unauthorized files or folders on the server.

¿Qué gravedad tiene CWE-32?

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-32?

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

¿Cómo puedo prevenir CWE-32?

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…

¿Cómo detecta y corrige Plexicus CWE-32?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-32 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-32?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/32.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-32

CWE-23 Padre

Relative Path Traversal

This vulnerability occurs when an application builds file paths using user-supplied input without properly validating or sanitizing it.…

CWE-24 Hermano

Path Traversal: '../filedir'

Path traversal, often called directory traversal, occurs when an application builds a file path using user input without properly blocking…

CWE-25 Hermano

Path Traversal: '/../filedir'

This vulnerability, often called directory traversal, occurs when an application builds a file path using user input without properly…

CWE-26 Hermano

Path Traversal: '/dir/../filename'

This vulnerability occurs when an application builds a file path using user input but fails to properly block directory traversal…

CWE-27 Hermano

Path Traversal: 'dir/../../filename'

This vulnerability occurs when an application builds file paths using user input but fails to properly block sequences like…

CWE-28 Hermano

Path Traversal: '..\filedir'

This vulnerability occurs when an application builds a file path using user input but fails to block or properly handle '..\' sequences.…

CWE-29 Hermano

Path Traversal: '\..\filename'

This vulnerability occurs when an application builds file paths using user input but fails to block '\..\filename' sequences. Attackers…

CWE-30 Hermano

Path Traversal: '\dir\..\filename'

This vulnerability occurs when an application builds file paths using user input but fails to properly sanitize sequences like…

CWE-31 Hermano

Path Traversal: 'dir\..\..\filename'

This vulnerability occurs when an application builds file paths using user input but fails to properly block sequences like…

Recursos

Further reading

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