CWE-1209 Base Incomplete

Failure to Disable Reserved Bits

This vulnerability occurs when reserved bits in a hardware design are left active in production. Designers sometimes use these bits for debugging or future features, but if not disabled, attackers…

Definition

What is CWE-1209?

This vulnerability occurs when reserved bits in a hardware design are left active in production. Designers sometimes use these bits for debugging or future features, but if not disabled, attackers can manipulate them to compromise the hardware's state.

Reserved bits are placeholders in a hardware design intended for future use and should have no functional purpose in the current version. However, to accelerate development or testing, designers might secretly enable logic connected to these bits for debugging or to prototype new features. Leaving this logic active creates a hidden backdoor that attackers can discover and exploit. When these bits remain enabled in production hardware, an adversary with access can write to them to trigger this hidden logic. This allows them to bypass security controls, alter configurations, or force the hardware into unsupported and potentially harmful states that were never intended for the released product.

Auswirkungen in der Praxis

Real-world CVEs caused by CWE-1209

Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.

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 Verilog

Assume a hardware Intellectual Property (IP) has address space 0x0-0x0F for its configuration registers, with the last one labeled reserved (i.e. 0x0F). Therefore inside the Finite State Machine (FSM), the code is as follows:

Verwundbar Verilog

reg gpio_out = 0; //gpio should remain low for normal operation

 case (register_address)

```
   4'b1111 : //0x0F
  	 begin
  		 gpio_out = 1;
  	 end

Sicheres Codebeispiel

Secure Verilog

An adversary may perform writes to reserved address space in hopes of changing the behavior of the hardware. In the code above, the GPIO pin should remain low for normal operation. However, it can be asserted by accessing the reserved address space (0x0F). This may be a concern if the GPIO state is being used as an indicator of health (e.g. if asserted the hardware may respond by shutting down or resetting the system, which may not be the correct action the system should perform). In the code below, the condition "register_address = 0X0F" is commented out, and a default is provided that will catch any values of register_address not explicitly accounted for and take no action with regards to gpio_out. This means that an attacker who is able to write 0X0F to register_address will not enable any undocumented "features" in the process.

Sicher Verilog

reg gpio_out = 0; //gpio should remain low for normal operation

 case (register_address)

```
   //4'b1111 : //0x0F
   default: gpio_out = gpio_out;

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-1209

Architecture and Design / Implementation Include a feature to disable reserved bits.
Integration Any writes to these reserve bits are blocked (e.g., ignored, access-protected, etc.), or an exception can be asserted.

Erkennungssignale

How to detect CWE-1209

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-1209 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-1209?

Wie gravierend ist CWE-1209?

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-1209 betroffen?

MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, System on Chip.

Wie kann ich CWE-1209 verhindern?

Include a feature to disable reserved bits. Any writes to these reserve bits are blocked (e.g., ignored, access-protected, etc.), or an exception can be asserted.

Wie erkennt und behebt Plexicus CWE-1209?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-1209 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-1209?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/1209.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-1209

CWE-710 Parent

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CWE-1041 Sibling

Use of Redundant Code

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CWE-1044 Sibling

Architecture with Number of Horizontal Layers Outside of Expected Range

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CWE-1048 Sibling

Invokable Control Element with Large Number of Outward Calls

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CWE-1059 Sibling

Insufficient Technical Documentation

This weakness occurs when a software or hardware product lacks comprehensive technical documentation. Missing or incomplete details about…

CWE-1061 Sibling

Insufficient Encapsulation

This weakness occurs when a software component exposes too much of its internal workings, such as data structures or implementation logic.…

CWE-1065 Sibling

Runtime Resource Management Control Element in a Component Built to Run on Application Servers

This weakness occurs when an application built to run on a managed application server bypasses the server's high-level APIs and instead…

CWE-1066 Sibling

Missing Serialization Control Element

This weakness occurs when a class or data structure is marked as serializable but lacks the required control methods to properly handle…

CWE-1068 Sibling

Inconsistency Between Implementation and Documented Design

This weakness occurs when the actual code implementation deviates from the intended design described in its official documentation,…

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