CWE-841 Base Incomplet

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…

Définition

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.
Impact réel

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.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  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:

Exemple de code vulnérable

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.

Vulnérable 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
```
...*
Exemple de code sécurisé

Secure Python

Here is a fixed version of the above example:

Sécurisé 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.
Liste de contrôle de prévention

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.
Signaux de détection

How to detect CWE-841

SAST High

Exécuter une analyse statique (SAST) sur le code source à la recherche du motif non sécurisé dans le flux de données.

DAST Moderate

Exécuter des tests de sécurité applicative dynamique (DAST) contre le point de terminaison en ligne.

Runtime Moderate

Surveiller les journaux runtime pour détecter des traces d'exception inhabituelles, des entrées malformées ou des tentatives de contournement d'autorisation.

Code review Moderate

Revue de code : signaler tout nouveau code qui traite les entrées de cette surface sans utiliser les helpers du framework validés.

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-841 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement
Questions fréquentes

Frequently asked questions

Qu'est-ce que 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.

Quelle est la gravité de CWE-841 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-841 ?

MITRE n'a pas spécifié les plateformes affectées pour ce CWE — il peut s'appliquer à la plupart des stacks applicatives.

Comment puis-je prévenir 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.

Comment Plexicus détecte et corrige CWE-841 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-841 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-841 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/841.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-841

CWE-691 Parent

Insufficient Control Flow Management

This vulnerability occurs when a program's execution flow isn't properly managed, allowing attackers to bypass critical checks, trigger…

CWE-1265 Frère

Unintended Reentrant Invocation of Non-reentrant Code Via Nested Calls

This vulnerability occurs when a non-reentrant function is called, and during its execution, another call is triggered that unexpectedly…

CWE-1281 Frère

Sequence of Processor Instructions Leads to Unexpected Behavior

Certain sequences of valid and invalid processor instructions can cause the CPU to lock up or behave unpredictably, often requiring a hard…

CWE-362 Frère

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

A race condition occurs when multiple processes or threads access a shared resource simultaneously without proper coordination, creating a…

CWE-430 Frère

Deployment of Wrong Handler

This vulnerability occurs when a system incorrectly assigns or routes an object to the wrong processing component.

CWE-431 Frère

Missing Handler

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

CWE-662 Frère

Improper Synchronization

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

CWE-670 Frère

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 Frère

Incorrect Behavior Order

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

Ressources

Further reading

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