CWE-841 Base Incomplete

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…

Definition

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.
Auswirkungen in der Praxis

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.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  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:

Verwundbares Codebeispiel

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.

Verwundbar 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
```
...*
Sicheres Codebeispiel

Secure Python

Here is a fixed version of the above example:

Sicher 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.
Präventions-Checkliste

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.
Erkennungssignale

How to detect CWE-841

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-841 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen
Häufig gestellte Fragen

Frequently asked questions

Was ist 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.

Wie gravierend ist CWE-841?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-841 betroffen?

MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.

Wie kann ich CWE-841 verhindern?

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.

Wie erkennt und behebt Plexicus CWE-841?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-841 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-841?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/841.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

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 Sibling

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 Sibling

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 Sibling

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 Sibling

Deployment of Wrong Handler

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

CWE-431 Sibling

Missing Handler

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

CWE-662 Sibling

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 Sibling

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 Sibling

Incorrect Behavior Order

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

Ressourcen

Further reading

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