Ejecuta análisis estático (SAST) sobre el código buscando el patrón inseguro en el flujo de datos.
CWE-179 Base Incompleto
Incorrect Behavior Order: Early Validation
This vulnerability occurs when an application validates user input before applying security filters or data normalization. Attackers can exploit this order of operations by submitting specially…
Definición
What is CWE-179?
This vulnerability occurs when an application validates user input before applying security filters or data normalization. Attackers can exploit this order of operations by submitting specially crafted input that passes the initial validation but becomes malicious after the application's filters or canonicalization processes modify it.
To prevent this flaw, validation logic must always run after data normalization and cleansing steps. Common operations like URL decoding, removing whitespace, or converting character encodings can change the input's structure. If you check for threats before these transformations, you create a window where a harmless-looking payload can be altered into a dangerous command, SQL injection, or path traversal attack after it's already been approved.
Think of it as checking a guest's ID before they take off a disguise. The secure approach is to first standardize the input (e.g., decode all entities, resolve paths), then cleanse it, and finally validate the sanitized result against your security rules. This ensures you are evaluating the actual data that will be used by your application's core logic, closing the bypass opportunity.
Impacto en el mundo real
Real-world CVEs caused by CWE-179
-
Product allows remote attackers to view restricted files via an HTTP request containing a "*" (wildcard or asterisk) character.
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Product modifies the first two letters of a filename extension after performing a security check, which allows remote attackers to bypass authentication via a filename with a .ats extension instead of a .hts extension.
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Database consumes an extra character when processing a character that cannot be converted, which could remove an escape character from the query and make the application subject to SQL injection attacks.
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Overlaps "fakechild/../realchild"
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Product checks URI for "<" and other literal characters, but does it before hex decoding the URI, so "%3E" and other sequences are allowed.
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Directory traversal vulnerability allows remote attackers to read or modify arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a ".." sequence.
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Directory traversal vulnerability allows attackers to overwrite arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a ".." sequence.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
The following code attempts to validate a given input path by checking it against an allowlist and then return the canonical path. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".
- 2
The problem with the above code is that the validation step occurs before canonicalization occurs. An attacker could provide an input path of "/safe_dir/../" that would pass the validation step. However, the canonicalization process sees the double dot as a traversal to the parent directory and hence when canonicized the path would become just "/".
- 3
To avoid this problem, validation should occur after canonicalization takes place. In this case canonicalization occurs during the initialization of the File object. The code below fixes the issue.
- 4
This script creates a subdirectory within a user directory and sets the user as the owner.
- 5
While the script attempts to screen for '..' sequences, an attacker can submit a directory path including ".~.", which will then become ".." after the filtering step. This allows a Path Traversal (CWE-21) attack to occur.
Ejemplo de código vulnerable
Vulnerable Java
The following code attempts to validate a given input path by checking it against an allowlist and then return the canonical path. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".
String path = getInputPath();
if (path.startsWith("/safe_dir/"))
{
File f = new File(path);
return f.getCanonicalPath();
} Ejemplo de código seguro
Secure Java
To avoid this problem, validation should occur after canonicalization takes place. In this case canonicalization occurs during the initialization of the File object. The code below fixes the issue.
String path = getInputPath();
File f = new File(path);
if (f.getCanonicalPath().startsWith("/safe_dir/"))
{
return f.getCanonicalPath();
} 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-179
- 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-179
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-179 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-179?
¿Qué gravedad tiene CWE-179?
¿Qué lenguajes o plataformas se ven afectados por CWE-179?
¿Cómo puedo prevenir CWE-179?
¿Cómo detecta y corrige Plexicus CWE-179?
¿Dónde puedo aprender más sobre CWE-179?
Frequently asked questions
¿Qué es CWE-179?
This vulnerability occurs when an application validates user input before applying security filters or data normalization. Attackers can exploit this order of operations by submitting specially crafted input that passes the initial validation but becomes malicious after the application's filters or canonicalization processes modify it.
¿Qué gravedad tiene CWE-179?
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-179?
MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.
¿Cómo puedo prevenir CWE-179?
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.
¿Cómo detecta y corrige Plexicus CWE-179?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-179 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-179?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/179.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
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