Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
CWE-441 Class Draft
Unintended Proxy or Intermediary ('Confused Deputy')
A confused deputy vulnerability occurs when a system receives a request from a client and forwards it to an external destination without properly identifying the original source. This makes the…
Definition
What is CWE-441?
A confused deputy vulnerability occurs when a system receives a request from a client and forwards it to an external destination without properly identifying the original source. This makes the system appear to be the originator of the request, effectively turning it into an unintended proxy for the client.
Attackers exploit this flaw when they cannot reach a target system directly. By sending a malicious request to your vulnerable application, they can have it relayed to the protected target. Since the request now originates from your system's IP address and context, it can bypass network firewalls, IP-based allowlists, and hide the attacker's true location, enabling unauthorized access or actions.
This becomes a critical security issue only under specific conditions: your application must have higher privileges or different network access than the initial requester; the attacker must be blocked from contacting the target directly; and the attacker must be able to craft a request that your application forwards unintentionally. This often involves specifying an unexpected host, port, internal IP, or a restricted command within an otherwise permitted service request.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-441
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FTP bounce attack. The design of the protocol allows an attacker to modify the PORT command to cause the FTP server to connect to other machines besides the attacker's.
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RPC portmapper could redirect service requests from an attacker to another entity, which thinks the requests came from the portmapper.
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FTP server does not ensure that the IP address in a PORT command is the same as the FTP user's session, allowing port scanning by proxy.
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Web server allows attackers to request a URL from another server, including other ports, which allows proxied scanning.
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CGI script accepts and retrieves incoming URLs.
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Bounce attack allows access to TFTP from trusted side.
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Web-based mail program allows internal network scanning using a modified POP3 port number.
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URL-downloading library automatically follows redirects to file:// and scp:// URLs
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
Identifiziere einen Codepfad, der nicht vertrauenswürdige Eingaben ohne Validierung verarbeitet.
- 2
Erzeuge eine Payload, die das unsichere Verhalten auslöst — Injection, Traversal, Overflow oder Logik-Missbrauch.
- 3
Liefere die Payload über einen normalen Request aus und beobachte die Reaktion der Anwendung.
- 4
Iteriere, bis die Antwort Daten preisgibt, Angreifer-Code ausführt oder Berechtigungen eskaliert.
Verwundbares Codebeispiel
Vulnerable Other
A SoC contains a microcontroller (running ring-3 (least trusted ring) code), a Memory Mapped Input Output (MMIO) mapped IP core (containing design-house secrets), and a Direct Memory Access (DMA) controller, among several other compute elements and peripherals. The SoC implements access control to protect the registers in the IP core (which registers store the design-house secrets) from malicious, ring-3 (least trusted ring) code executing on the microcontroller. The DMA controller, however, is not blocked off from accessing the IP core for functional reasons.
The code in ring-3 (least trusted ring) of the microcontroller attempts to directly read the protected registers in IP core through MMIO transactions. However, this attempt is blocked due to the implemented access control. Now, the microcontroller configures the DMA core to transfer data from the protected registers to a memory region that it has access to. The DMA core, which is acting as an intermediary in this transaction, does not preserve the identity of the microcontroller and, instead, initiates a new transaction with its own identity. Since the DMA core has access, the transaction (and hence, the attack) is successful. Sicheres Codebeispiel
Secure Other
The weakness here is that the intermediary or the proxy agent did not ensure the immutability of the identity of the microcontroller initiating the transaction.
The DMA core forwards this transaction with the identity of the code executing on the microcontroller, which is the original initiator of the end-to-end transaction. Now the transaction is blocked, as a result of forwarding the identity of the true initiator which lacks the permission to access the confidential MMIO mapped IP core. 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-441
- Architecture and Design Enforce the use of strong mutual authentication mechanism between the two parties.
- Architecture and Design Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.
Erkennungssignale
How to detect CWE-441
CWE-441
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Häufig gestellte Fragen Was ist CWE-441?
Wie gravierend ist CWE-441?
Welche Sprachen oder Plattformen sind von CWE-441 betroffen?
Wie kann ich CWE-441 verhindern?
Wie erkennt und behebt Plexicus CWE-441?
Wo erfahre ich mehr über CWE-441?
Frequently asked questions
Was ist CWE-441?
A confused deputy vulnerability occurs when a system receives a request from a client and forwards it to an external destination without properly identifying the original source. This makes the system appear to be the originator of the request, effectively turning it into an unintended proxy for the client.
Wie gravierend ist CWE-441?
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-441 betroffen?
MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Not Technology-Specific.
Wie kann ich CWE-441 verhindern?
Enforce the use of strong mutual authentication mechanism between the two parties. Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.
Wie erkennt und behebt Plexicus CWE-441?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-441 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-441?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/441.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
Weaknesses related to CWE-441
CWE-610 Parent
Externally Controlled Reference to a Resource in Another Sphere
This vulnerability occurs when an application uses user-supplied input to reference a resource located outside its intended security…
CWE-1021 Sibling
Improper Restriction of Rendered UI Layers or Frames
This vulnerability occurs when a web application fails to properly control whether its pages can be embedded within frames or UI layers…
CWE-15 Sibling
External Control of System or Configuration Setting
This vulnerability occurs when an application allows users to directly modify critical system settings or configuration values from an…
CWE-384 Sibling
Session Fixation
Session fixation occurs when an application authenticates a user without first destroying the previous session ID. This allows an attacker…
CWE-470 Sibling
Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
This vulnerability occurs when an application uses unvalidated external input, like a URL parameter or form field, to dynamically decide…
CWE-601 Sibling
URL Redirection to Untrusted Site ('Open Redirect')
An open redirect vulnerability occurs when a web application uses unvalidated user input to determine the destination of a redirect,…
CWE-611 Sibling
Improper Restriction of XML External Entity Reference
This vulnerability occurs when an application processes XML input without properly restricting external entity references. Attackers can…
CWE-73 Sibling
External Control of File Name or Path
This vulnerability occurs when an application uses unvalidated user input to construct file or directory paths for filesystem operations.
CWE-918 Sibling
Server-Side Request Forgery (SSRF)
Server-Side Request Forgery (SSRF) occurs when a web application fetches a remote resource based on user-controlled input, but fails to…
Ressourcen
Further reading
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