CWE-841 Base Incompleto

Improper Enforcement of Behavioral Workflow

This weakness occurs when an application requires a user to follow a specific sequence of actions, but fails to enforce that order. Attackers can exploit this by skipping steps, performing actions…

Definição

What is CWE-841?

This weakness occurs when an application requires a user to follow a specific sequence of actions, but fails to enforce that order. Attackers can exploit this by skipping steps, performing actions out of sequence, or interrupting the flow, which can corrupt the business logic or put the system into an invalid state.
When a multi-step process isn't strictly sequenced, attackers can manipulate it to bypass critical checks. For instance, a file-sharing server might require a username, then a password, before allowing a file transfer. If it accepts a transfer command immediately after a password—without a username—the core authentication workflow is broken, potentially granting unauthorized access. Proper workflow enforcement means ensuring steps happen in the correct order, no required steps are omitted, processes aren't maliciously interrupted, and actions occur within a reasonable timeframe. This is distinct from software itself executing steps incorrectly (CWE-696); here, the flaw is in failing to control the *user's* or *client's* path through the required behaviors.
Impacto no mundo real

Real-world CVEs caused by CWE-841

  • CVE-2011-0348

    Bypass of access/billing restrictions by sending traffic to an unrestricted destination before sending to a restricted destination.

  • CVE-2007-3012

    Attacker can access portions of a restricted page by canceling out of a dialog.

  • CVE-2009-5056

    Ticket-tracking system does not enforce a permission setting.

  • CVE-2004-2164

    Shopping cart does not close a database connection when user restores a previous order, leading to connection exhaustion.

  • CVE-2003-0777

    Chain: product does not properly handle dropped connections, leading to missing NULL terminator (CWE-170) and segmentation fault.

  • CVE-2005-3327

    Chain: Authentication bypass by skipping the first startup step as required by the protocol.

  • CVE-2004-0829

    Chain: File server crashes when sent a "find next" request without an initial "find first."

  • CVE-2010-2620

    FTP server allows remote attackers to bypass authentication by sending (1) LIST, (2) RETR, (3) STOR, or other commands without performing the required login steps first.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    This code is part of an FTP server and deals with various commands that could be sent by a user. It is intended that a user must successfully login before performing any other action such as retrieving or listing files.

  2. 2

    The server correctly avoids sending files to a user that isn't logged in and doesn't own the file. However, the server will incorrectly list the files in any directory without confirming the command came from an authenticated user, and that the user is authorized to see the directory's contents.

  3. 3

    Here is a fixed version of the above example:

Exemplo de código vulnerável

Vulnerable Python

This code is part of an FTP server and deals with various commands that could be sent by a user. It is intended that a user must successfully login before performing any other action such as retrieving or listing files.

Vulnerável Python 
def dispatchCommand(command, user, args):
  		if command == 'Login':
  			loginUser(args)
  			return
```
# user has requested a file* 
  		if command == 'Retrieve_file': 
  		```
  			 if authenticated(user) and ownsFile(user,args): 
  				sendFile(args)
  				return
  		if command == 'List_files':
  			listFiles(args)
  			return
```
...*
Exemplo de código seguro

Secure Python

Here is a fixed version of the above example:

Seguro Python 
def dispatchCommand(command, user, args):
```
...* 
  		if command == 'List_files':
  		```
  			if authenticated(user) and ownsDirectory(user,args):
  				listFiles(args)
  				return
```
...*
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-841

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Sinais de deteção

How to detect CWE-841

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-841 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.

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Perguntas frequentes

Frequently asked questions

O que é o CWE-841?

This weakness occurs when an application requires a user to follow a specific sequence of actions, but fails to enforce that order. Attackers can exploit this by skipping steps, performing actions out of sequence, or interrupting the flow, which can corrupt the business logic or put the system into an invalid state.

Qual a gravidade do CWE-841?

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-841?

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

Como posso prevenir o CWE-841?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

Como é que o Plexicus deteta e corrige o CWE-841?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-841 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-841?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/841.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-841

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CWE-430 Irmão

Deployment of Wrong Handler

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CWE-431 Irmão

Missing Handler

This vulnerability occurs when a software component lacks the necessary code to properly handle an error or unexpected event.

CWE-662 Irmão

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This vulnerability occurs when a multi-threaded or multi-process application allows shared resources to be accessed by multiple threads or…

CWE-670 Irmão

Always-Incorrect Control Flow Implementation

This weakness occurs when a section of code is structured in a way that always executes incorrectly, regardless of input or conditions.…

CWE-696 Irmão

Incorrect Behavior Order

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

Recursos

Further reading

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