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.
CWE-1296 Base Incomplete
Incorrect Chaining or Granularity of Debug Components
This vulnerability occurs when hardware debug components, such as test ports and scan chains, are incorrectly connected or organized within a chip's design. This misconfiguration can create…
Definition
What is CWE-1296?
This vulnerability occurs when hardware debug components, such as test ports and scan chains, are incorrectly connected or organized within a chip's design. This misconfiguration can create unintended access paths, potentially exposing sensitive internal data or functions.
Modern chips incorporate specialized debug components like Test Access Ports (TAPs) for boundary scans, internal scan cells for stimulus/response testing, and custom tracing hubs for monitoring. If these elements are chained together incorrectly or organized with improper granularity during the design phase, it breaks the intended security model of the debug infrastructure.
This design or synthesis error creates hidden backdoors or elevates access permissions within the chip. Attackers could exploit these flawed connections to bypass security controls, extract cryptographic keys, or manipulate the chip's internal state, turning vital debugging features into serious security liabilities.
Real-world impact
Real-world CVEs caused by CWE-1296
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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 Wire Debug (SWD) commands because there is a race condition between full initialization of the SWD interface and the setup of flash protection.
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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 third desktop after a series of operations in ADB mode. (Vulnerability ID: HWPSIRT-2019-10114).
How attackers exploit it
Step-by-step attacker path
- 1
The following example shows how an attacker can take advantage of incorrect chaining or missing granularity of debug components.
- 2
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.
- 3
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.
Vulnerable code example
Vulnerable pseudo
MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} 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-1296
- Implementation Ensure that debug components are properly chained and their granularity is maintained at different authentication levels.
Detection signals
How to detect CWE-1296
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.
CWE-1296
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Frequently asked questions What is CWE-1296?
How serious is CWE-1296?
What languages or platforms are affected by CWE-1296?
How can I prevent CWE-1296?
How does Plexicus detect and fix CWE-1296?
Where can I learn more about CWE-1296?
Frequently asked questions
What is CWE-1296?
This vulnerability occurs when hardware debug components, such as test ports and scan chains, are incorrectly connected or organized within a chip's design. This misconfiguration can create unintended access paths, potentially exposing sensitive internal data or functions.
How serious is CWE-1296?
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-1296?
MITRE lists the following affected platforms: Verilog, VHDL, Not OS-Specific, Not Architecture-Specific, Processor Hardware, Not Technology-Specific.
How can I prevent CWE-1296?
Ensure that debug components are properly chained and their granularity is maintained at different authentication levels.
How does Plexicus detect and fix CWE-1296?
Plexicus's SAST engine matches the data-flow signature for CWE-1296 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-1296?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1296.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-1296
CWE-284 Parent
Improper Access Control
The software fails to properly limit who can access a resource, allowing unauthorized users or systems to interact with it.
CWE-1191 Sibling
On-Chip Debug and Test Interface With Improper Access Control
This vulnerability occurs when a hardware chip's debug or test interface (like JTAG) lacks proper access controls. Without correct…
CWE-1220 Sibling
Insufficient Granularity of Access Control
This vulnerability occurs when a system's access controls are too broad, allowing unauthorized users or processes to read or modify…
CWE-1224 Sibling
Improper Restriction of Write-Once Bit Fields
This vulnerability occurs when hardware write-once protection mechanisms, often called 'sticky bits,' are incorrectly implemented,…
CWE-1231 Sibling
Improper Prevention of Lock Bit Modification
This vulnerability occurs when hardware or firmware uses a lock bit to protect critical system registers or memory regions, but fails to…
CWE-1233 Sibling
Security-Sensitive Hardware Controls with Missing Lock Bit Protection
This vulnerability occurs when a hardware device uses a lock bit to protect critical configuration registers, but the lock fails to…
CWE-1252 Sibling
CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations
This vulnerability occurs when a CPU's hardware is not set up to enforce a strict separation between writing data to memory and executing…
CWE-1257 Sibling
Improper Access Control Applied to Mirrored or Aliased Memory Regions
This vulnerability occurs when a hardware design maps the same physical memory to multiple addresses (aliasing or mirroring) but fails to…
CWE-1259 Sibling
Improper Restriction of Security Token Assignment
This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly secure its Security Token mechanism. These tokens control which…
Resources
Further reading
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