Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.
CWE-40 Variante Borrador
Path Traversal: '\\UNC\share\name\' (Windows UNC Share)
This vulnerability occurs when an application accepts user input containing a Windows UNC share path (like '\\UNC\share\name') without proper validation, allowing attackers to redirect file…
Definición
What is CWE-40?
This vulnerability occurs when an application accepts user input containing a Windows UNC share path (like '\\UNC\share\name') without proper validation, allowing attackers to redirect file operations to unintended network locations or arbitrary files.
Windows UNC (Universal Naming Convention) paths begin with double backslashes (\\), followed by a server name and share name, enabling network file access. When an application blindly trusts user input containing these paths, attackers can manipulate file reads, writes, or includes to target sensitive files on remote servers or internal network shares they shouldn't have access to.
To prevent this, developers should treat UNC paths with the same suspicion as local file paths. Implement strict allow-lists of permitted directories, normalize paths before validation, and run applications with minimal network permissions. Always validate and sanitize user input that references file systems, whether local or networked.
Impacto en el mundo real
Real-world CVEs caused by CWE-40
-
FTP server allows a remote attacker to retrieve privileged web server system information by specifying arbitrary paths in the UNC format (\\computername\sharename).
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.
// 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
// 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-40
- 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-40
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.
Plexicus detecta automáticamente CWE-40 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.
Preguntas frecuentes ¿Qué es CWE-40?
¿Qué gravedad tiene CWE-40?
¿Qué lenguajes o plataformas se ven afectados por CWE-40?
¿Cómo puedo prevenir CWE-40?
¿Cómo detecta y corrige Plexicus CWE-40?
¿Dónde puedo aprender más sobre CWE-40?
Frequently asked questions
¿Qué es CWE-40?
This vulnerability occurs when an application accepts user input containing a Windows UNC share path (like '\\UNC\share\name') without proper validation, allowing attackers to redirect file operations to unintended network locations or arbitrary files.
¿Qué gravedad tiene CWE-40?
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-40?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-40?
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-40?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-40 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-40?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/40.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-40
CWE-36 Padre
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Path Traversal: '/absolute/pathname/here'
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CWE-38 Hermano
Path Traversal: '\absolute\pathname\here'
This vulnerability occurs when an application accepts user-supplied input containing Windows-style absolute paths (like…
CWE-39 Hermano
Path Traversal: 'C:dirname'
This vulnerability occurs when an application accepts user input containing Windows drive letters (like 'C:dirname') without proper…
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