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…

Definição

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 no mundo real

Real-world CVEs caused by CWE-179

  • CVE-2002-0433

    Product allows remote attackers to view restricted files via an HTTP request containing a "*" (wildcard or asterisk) character.

  • CVE-2003-0332

    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.

  • CVE-2002-0802

    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.

  • CVE-2000-0191

    Overlaps "fakechild/../realchild"

  • CVE-2004-2363

    Product checks URI for "<" and other literal characters, but does it before hex decoding the URI, so "%3E" and other sequences are allowed.

  • CVE-2002-0934

    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.

  • CVE-2003-0282

    Directory traversal vulnerability allows attackers to overwrite arbitrary files via invalid characters between two . (dot) characters, which are filtered and result in a ".." sequence.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 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. 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. 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. 4

    This script creates a subdirectory within a user directory and sets the user as the owner.

  5. 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.

Exemplo de código vulnerável

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/".

Vulnerável Java 
String path = getInputPath();
  if (path.startsWith("/safe_dir/"))
  {
  	File f = new File(path);
  	return f.getCanonicalPath();
  }
Exemplo 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.

Seguro Java 
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 verificação de prevenção

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.
Sinais de deteção

How to detect CWE-179

SAST High

Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.

DAST Moderate

Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.

Runtime Moderate

Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.

Code review Moderate

Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-179 e abre um PR de correção em menos de 60 segundos.

O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.

Obter uma demonstração Experimente o Plexicus gratuitamente
Perguntas frequentes

Frequently asked questions

O que é o 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.

Qual a gravidade do CWE-179?

A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.

Que linguagens ou plataformas são afetadas pelo CWE-179?

A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.

Como posso prevenir o 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.

Como é que o Plexicus deteta e corrige o CWE-179?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-179 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.

Onde posso saber mais sobre o CWE-179?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/179.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-179

CWE-696 Pai

Incorrect Behavior Order

This weakness occurs when a system executes multiple dependent actions in the wrong sequence, leading to unexpected and potentially…

CWE-1190 Irmão

DMA Device Enabled Too Early in Boot Phase

This vulnerability occurs when a device with Direct Memory Access (DMA) capability is activated before the system's security settings are…

CWE-1193 Irmão

Power-On of Untrusted Execution Core Before Enabling Fabric Access Control

This vulnerability occurs when a system powers up hardware components containing untrusted firmware before establishing critical security…

CWE-1279 Irmão

Cryptographic Operations are run Before Supporting Units are Ready

This vulnerability occurs when cryptographic processes start before their required dependencies are properly initialized and ready to…

CWE-1280 Irmão

Access Control Check Implemented After Asset is Accessed

This vulnerability occurs when a hardware-based security check runs after the protected resource has already been accessed, creating a…

CWE-408 Irmão

Incorrect Behavior Order: Early Amplification

This vulnerability occurs when a system allows a user to trigger a resource-intensive operation before verifying their identity or…

CWE-551 Irmão

Incorrect Behavior Order: Authorization Before Parsing and Canonicalization

This vulnerability occurs when a web server checks access permissions before fully processing and normalizing a URL, potentially allowing…

CWE-180 Filho

Incorrect Behavior Order: Validate Before Canonicalize

This vulnerability occurs when a system checks user input for malicious content before standardizing its format, allowing specially…

CWE-181 Filho

Incorrect Behavior Order: Validate Before Filter

This vulnerability occurs when a system checks user input for validity before cleaning or filtering it. This flawed sequence allows…

Recursos

Further reading

Pronto quando você estiver

Pare de pagar por desenvolvedor.
Comece a fechar o ciclo.

O Plexicus é o ASPM nativo de IA que verifica, filtra, corrige, pentesta e explica — de forma autónoma. Programadores ilimitados, repos ilimitados, ações de IA de utilização justa. Nível gratuito real, €269/mo anual quando estiver pronto.

Começar grátis Reservar uma demo