CWE-1296: Incorrect Chaining or Granularity of Debug Components

Description

The product's debug components contain incorrect chaining or granularity of debug components.

For debugging and troubleshooting a chip, several hardware design elements are often implemented, including: Logic errors during design or synthesis could misconfigure the interconnection of the debug components, which could allow unintended access permissions.

Potential Impact

Confidentiality, Integrity, Access Control, Authentication, Authorization, Availability, Accountability

Gain Privileges or Assume Identity, Bypass Protection Mechanism, Execute Unauthorized Code or Commands, Modify Memory, Modify Files or Directories

Demonstrative Examples

The following example shows how an attacker can take advantage of incorrect chaining or missing granularity of debug components.
In a System-on-Chip (SoC), the user might be able to access the SoC-level TAP with a certain level of authorization. However, this access should not also grant access to all of the internal TAPs (e.g., Core). Separately, if any of the internal TAPs is also stitched to the TAP chain when it should not be because of a logic error, then an attacker can access the internal TAPs as well and execute commands there.
As a related example, suppose there is a hierarchy of TAPs (TAP_A is connected to TAP_B and TAP_C, then TAP_B is connected to TAP_D and TAP_E, then TAP_C is connected to TAP_F and TAP_G, etc.).  Architecture mandates that the user have one set of credentials for just accessing TAP_A, another set of credentials for accessing TAP_B and TAP_C, etc. However, if, during implementation, the designer mistakenly implements a daisy-chained TAP where all the TAPs are connected in a single TAP chain without the hierarchical structure, the correct granularity of debug components is not implemented and the attacker can gain unauthorized access.

Mitigations & Prevention

Implementation

Ensure that debug components are properly chained and their granularity is maintained at different authentication levels.

Detection Methods

Architecture or Design Review High — Appropriate Post-Si tests should be carried out at various authorization levels to ensure that debug components are properly chained and accessible only to users with appropriate credentials.
Dynamic Analysis with Manual Results Interpretation High — Appropriate Post-Si tests should be carried out at various authorization levels to ensure that debug components are properly chained and accessible only to users with appropriate credentials.

Real-World CVE Examples

CVE ID	Description
CVE-2017-18347	Incorrect access control in RDP Level 1 on STMicroelectronics STM32F0 series devices allows physically present attackers to extract the device's protected firmware via a special sequence of Serial Wir
CVE-2020-1791	There is an improper authorization vulnerability in several smartphones. The system has a logic-judging error, and, under certain scenarios, a successful exploit could allow the attacker to switch to

Frequently Asked Questions

What is CWE-1296?

CWE-1296 (Incorrect Chaining or Granularity of Debug Components) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The product's debug components contain incorrect chaining or granularity of debug components.

How can CWE-1296 be exploited?

Attackers can exploit CWE-1296 (Incorrect Chaining or Granularity of Debug Components) to gain privileges or assume identity, bypass protection mechanism, execute unauthorized code or commands, modify memory, modify files or directories. This weakness is typically introduced during the Implementation phase of software development.

How do I prevent CWE-1296?

Key mitigations include: Ensure that debug components are properly chained and their granularity is maintained at different authentication levels.

What is the severity of CWE-1296?

CWE-1296 is classified as a Base-level weakness (Medium abstraction). It has been observed in 2 real-world CVEs.