CWE-1259: Improper Restriction of Security Token Assignment

Extended Description

Systems-On-A-Chip (Integrated circuits and hardware engines) implement Security Tokens to differentiate and identify which actions originated from which agent. These actions may be one of the directives: 'read', 'write', 'program', 'reset', 'fetch', 'compute', etc. Security Tokens are assigned to every agent in the System that is capable of generating an action or receiving an action from another agent. Multiple Security Tokens may be assigned to an agent and may be unique based on the agent's trust level or allowed privileges. Since the Security Tokens are integral for the maintenance of security in an SoC, they need to be protected properly. A common weakness afflicting Security Tokens is improperly restricting the assignment to trusted components.

Code Examples & CVEs

Demonstrative Examples

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.

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

BadOther

The Aux-controller could program its Security Token to "1" from "2".

GoodOther

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

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-1259 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-1259, Improper Restriction of Security Token Assignment, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Improper Restriction of Security Token Assignment during Architecture and Design

MITRE associates mitigation with Architecture and Design, and Implementation; recorded impacts include Modify Files or Directories, Execute Unauthorized Code or Commands, Bypass Protection Mechanism, Gain Privileges or Assume Identity, and Modify Memory; the entry maps to CAPEC-121, and CAPEC-681. Use these source-defined anchors to turn CWE-1259 into implementation, review, and verification checks for the affected component.

CWE-1259: Improper Restriction of Security Token Assignment — MITRE CWE

Triage CWE-1259 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-1259, Improper Restriction of Security Token Assignment, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-1259

Apply MITRE's full root-cause mapping guidance when using CWE-1259, Improper Restriction of Security Token Assignment. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-1259 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-1259, Improper Restriction of Security Token Assignment. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-1259: Improper Restriction of Security Token Assignment?+

CWE-1259: Improper Restriction of Security Token Assignment is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The System-On-A-Chip (SoC) implements a Security Token mechanism to differentiate what actions are allowed or disallowed when a transaction originates from an entity. However, the Security Tokens are improperly protected. Systems-On-A-Chip (Integrated circuits and hardware engines) implement Security Tokens to differentiate and identify which actions originated from which agent. These actions may be one of the directives: 'read', 'write', 'program', 'reset', 'fetch', 'compute', etc. Security Tokens are assigned to every agent in the System that is capable of generating an action or receiving an action from another agent. Multiple Security Tokens may be assigned to an agent and may be unique based on the agent's trust level or allowed privileges. Since the Security Tokens are integral for the maintenance of security in an SoC, they need to be protected properly. A common weakness afflicting Security Tokens is improperly restricting the assignment to trusted components.

What are the security consequences of Improper Restriction of Security Token Assignment?+

If exploited, CWE-1259 (Improper Restriction of Security Token Assignment) it can compromise Confidentiality, Integrity, Availability and Access Control, leading to outcomes such as Modify Files or Directories, Execute Unauthorized Code or Commands, Bypass Protection Mechanism, Gain Privileges or Assume Identity, Modify Memory and DoS: Crash, Exit, or Restart.

How do you prevent or mitigate Improper Restriction of Security Token Assignment?+

Recommended mitigations for CWE-1259 include: 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.

Which programming languages are affected by Improper Restriction of Security Token Assignment?+

CWE-1259 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-1259 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-1259: Improper Restriction of Security Token Assignment

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