CWE-1259 Base Incomplete

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 actions different system components are allowed to perform,…

Definition

What is CWE-1259?

This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly secure its Security Token mechanism. These tokens control which actions different system components are allowed to perform, but inadequate protection allows them to be manipulated.
Security Tokens act as digital IDs within a System-on-a-Chip, determining what operations each component can execute—such as read, write, program, or reset. Each agent in the system receives one or more tokens based on its trust level and privileges. Since these tokens directly enforce security boundaries, any weakness in their assignment or protection compromises the entire system's integrity. When token assignment isn't properly restricted, malicious agents can reprogram or spoof tokens to impersonate trusted components. This allows attackers to bypass privilege checks and perform unauthorized actions, effectively breaking the hardware's security model. Proper implementation must ensure tokens are immutable and only assignable by trusted system logic.
Real-world impact

Real-world CVEs caused by CWE-1259

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

How attackers exploit it

Step-by-step attacker path

  1. 1

    For example, consider a system with a register for storing an AES key for encryption and decryption. The key is of 128 bits implemented as a set of four 32-bit registers. The key register assets have an associated control register, AES_KEY_ACCESS_POLICY, which provides the necessary access controls. This access-policy register defines which agents may engage in a transaction, and the type of transaction, with the AES-key registers. Each bit in this 32-bit register defines a security Token. There could be a maximum of 32 security Tokens that are allowed access to the AES-key registers. The number of the bit when set (i.e., "1") allows respective action from an agent whose identity matches the number of the bit and, if "0" (i.e., Clear), disallows the respective action to that corresponding agent.

  2. 2

    Let's assume the system has two agents: a Main-controller and an Aux-controller. The respective Security Tokens are "1" and "2". | Register | Description | Default | | --- | --- | --- | | AES_ENC_DEC_KEY_0 | AES key [0:31] for encryption or decryption | 0x00000000 | | AES_ENC_DEC_KEY_1 | AES key [32:63] for encryption or decryption | 0x00000000 | | AES_ENC_DEC_KEY_2 | AES key [64:95] for encryption or decryption | 0x00000000 | | AES_ENC_DEC_KEY_3 | AES key [96:127] for encryption or decryption | 0x00000000 | | AES_KEY_ACCESS_POLICY | AES key access register [31:0] | 0x00000002 |

  3. 3

    An agent with Security Token "1" has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_3 registers. As per the above access policy, the AES-Key-access policy allows access to the AES-key registers if the security Token is "1".

  4. 4

    The SoC does not properly protect the Security Token of the agents, and, hence, the Aux-controller in the above example can spoof the transaction (i.e., send the transaction as if it is coming from the Main-controller to access the AES-Key registers)

Vulnerable code example

Vulnerable Other

An agent with Security Token "1" has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_3 registers. As per the above access policy, the AES-Key-access policy allows access to the AES-key registers if the security Token is "1".

Vulnerable Other 
The Aux-controller could program its Security Token to "1" from "2".
Secure code example

Secure Other

The SoC does not properly protect the Security Token of the agents, and, hence, the Aux-controller in the above example can spoof the transaction (i.e., send the transaction as if it is coming from the Main-controller to access the AES-Key registers)

Secure Other 
The SoC needs to protect the Security Tokens. None of the agents in the SoC should have the ability to change the Security Token.
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-1259

  • Architecture and Design / Implementation - Security Token assignment review checks for design inconsistency and common weaknesses. - Security-Token definition and programming flow is tested in both pre-silicon and post-silicon testing.
Detection signals

How to detect CWE-1259

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-1259 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

Frequently asked questions

What is CWE-1259?

This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly secure its Security Token mechanism. These tokens control which actions different system components are allowed to perform, but inadequate protection allows them to be manipulated.

How serious is CWE-1259?

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-1259?

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

How can I prevent CWE-1259?

- Security Token assignment review checks for design inconsistency and common weaknesses. - Security-Token definition and programming flow is tested in both pre-silicon and post-silicon testing.

How does Plexicus detect and fix CWE-1259?

Plexicus's SAST engine matches the data-flow signature for CWE-1259 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-1259?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1259.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-1259

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-1260 Sibling

Improper Handling of Overlap Between Protected Memory Ranges

This vulnerability occurs when a system incorrectly allows different memory protection ranges to overlap. This flaw can let attackers…

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Further reading

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