CWE-1276 Base Incomplete

Hardware Child Block Incorrectly Connected to Parent System

This vulnerability occurs when a hardware component (IP block) is wired incorrectly to the main system, creating hidden security flaws even if basic functions appear to work.

Definition

What is CWE-1276?

This vulnerability occurs when a hardware component (IP block) is wired incorrectly to the main system, creating hidden security flaws even if basic functions appear to work.

For a system-on-chip (SoC) to operate securely, its internal hardware blocks must communicate with the parent system using the correct control and data signals. An incorrect connection—like linking a reset pin to the wrong system controller—can bypass critical security boundaries. While the device might still boot and run, this miswiring opens a backdoor that attackers can exploit to tamper with sensitive data or operations. Consider a block designed to only clear its data during a full system power cycle. If its reset line is mistakenly connected to a software-controlled debug reset, a privileged process or an attacker gaining software access could trigger an unauthorized reset. This violates the hardware's data integrity guarantees, potentially leaking secrets or corrupting secure state, all while the system seems to function normally from a user's perspective.

Real-world impact

Real-world CVEs caused by CWE-1276

No public CVE references are linked to this CWE in MITRE's catalog yet.

How attackers exploit it

Step-by-step attacker path

1
Many SoCs use hardware to partition system resources between trusted and un-trusted entities. One example of this concept is the Arm TrustZone, in which the processor and all security-aware IP attempt to isolate resources based on the status of a privilege bit. This privilege bit is part of the input interface in all TrustZone-aware IP. If this privilege bit is accidentally grounded or left unconnected when the IP is instantiated, privilege escalation of all input data may occur.
2
In the Verilog code below, the security level input to the TrustZone aware peripheral is correctly driven by an appropriate signal instead of being grounded.
3
Here is a code snippet from the Ariane core module in the HACK@DAC'21 Openpiton SoC [REF-1362]. To ensure full functional correctness, developers connect the ports with names. However, in some cases developers forget to connect some of these ports to the desired signals in the parent module. These mistakes by developers can lead to incorrect functional behavior or, in some cases, introduce security vulnerabilities.
4
In the above example from HACK@DAC'21, since interrupt signals are not properly connected, the CSR module will fail to send notifications in the event of interrupts. Consequently, critical information in CSR registers that should be flushed or modified in response to an interrupt won't be updated. These vulnerabilities can potentially result in information leakage across various privilege levels.
5
To address the aforementioned vulnerability, developers must follow a two-step approach. First, they should ensure that all module signals are properly connected. This can often be facilitated using automated tools, and many simulators and sanitizer tools issue warnings when a signal remains unconnected or floats. Second, it is imperative to validate that the signals connected to a module align with the specifications. In the provided example, the developer should establish the correct connection of interrupt signals from the parent module (Ariane core) to the child module (csr_regfile) [REF-1363].

Vulnerable code example

Vulnerable Verilog

Many SoCs use hardware to partition system resources between trusted and un-trusted entities. One example of this concept is the Arm TrustZone, in which the processor and all security-aware IP attempt to isolate resources based on the status of a privilege bit. This privilege bit is part of the input interface in all TrustZone-aware IP. If this privilege bit is accidentally grounded or left unconnected when the IP is instantiated, privilege escalation of all input data may occur.

Vulnerable Verilog

// IP definition
 module tz_peripheral(clk, reset, data_in, data_in_security_level, ...);

```
   input clk, reset;
   input [31:0] data_in;
   input data_in_security_level;
   ...
 endmodule
 // Instantiation of IP in a parent system
 module soc(...)
   ...
   tz_peripheral u_tz_peripheral(
  	 .clk(clk),
  	 .rst(rst),
  	 .data_in(rdata),
  	 //Copy-and-paste error or typo grounds data_in_security_level (in this example 0=secure, 1=non-secure) effectively promoting all data to "secure")
  	 .data_in_security_level(1'b0),
   );
   ...
 endmodule

Secure code example

Secure Verilog

In the Verilog code below, the security level input to the TrustZone aware peripheral is correctly driven by an appropriate signal instead of being grounded.

Secure Verilog

// Instantiation of IP in a parent system
 module soc(...)

```
   ...
   tz_peripheral u_tz_peripheral(
  	 .clk(clk),
  	 .rst(rst),
  	 .data_in(rdata),
  	 // This port is no longer grounded, but instead driven by the appropriate signal
  	 .data_in_security_level(rdata_security_level),
   );
   ...
 endmodule

What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.

Prevention checklist

How to prevent CWE-1276

Testing System-level verification may be used to ensure that components are correctly connected and that design security requirements are not violated due to interactions between various IP blocks.

Detection signals

How to detect CWE-1276

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-1276 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

What is CWE-1276?

This vulnerability occurs when a hardware component (IP block) is wired incorrectly to the main system, creating hidden security flaws even if basic functions appear to work.

How serious is CWE-1276?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-1276?

MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Not Technology-Specific.

How can I prevent CWE-1276?

System-level verification may be used to ensure that components are correctly connected and that design security requirements are not violated due to interactions between various IP blocks.

How does Plexicus detect and fix CWE-1276?

Plexicus's SAST engine matches the data-flow signature for CWE-1276 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-1276?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1276.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-1276

CWE-284 Parent

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Hardware Child Block Incorrectly Connected to Parent System

What is CWE-1276?

Real-world CVEs caused by CWE-1276

Step-by-step attacker path

Vulnerable Verilog

Secure Verilog

How to prevent CWE-1276

How to detect CWE-1276

Plexicus auto-detects CWE-1276 and opens a fix PR in under 60 seconds.

Frequently asked questions

Weaknesses related to CWE-1276

Improper Access Control

On-Chip Debug and Test Interface With Improper Access Control

Insufficient Granularity of Access Control

Improper Restriction of Write-Once Bit Fields

Improper Prevention of Lock Bit Modification

Security-Sensitive Hardware Controls with Missing Lock Bit Protection

CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations

Improper Access Control Applied to Mirrored or Aliased Memory Regions

Improper Restriction of Security Token Assignment

Further reading

Don't Let Security
Weigh You Down.

Hardware Child Block Incorrectly Connected to Parent System

What is CWE-1276?

Real-world CVEs caused by CWE-1276

Step-by-step attacker path

Vulnerable Verilog

Secure Verilog

How to prevent CWE-1276

How to detect CWE-1276

Plexicus auto-detects CWE-1276 and opens a fix PR in under 60 seconds.

Frequently asked questions

Weaknesses related to CWE-1276

Improper Access Control

On-Chip Debug and Test Interface With Improper Access Control

Insufficient Granularity of Access Control

Improper Restriction of Write-Once Bit Fields

Improper Prevention of Lock Bit Modification

Security-Sensitive Hardware Controls with Missing Lock Bit Protection

CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations

Improper Access Control Applied to Mirrored or Aliased Memory Regions

Improper Restriction of Security Token Assignment

Further reading

Don't Let SecurityWeigh You Down.

Don't Let Security
Weigh You Down.