Cybersecurity is becoming a transparency challenge
For safety-critical embedded systems, cybersecurity is about understanding the software at the heart of a product, managing its vulnerabilities and maintaining visibility into how security has been addressed throughout its development lifecycle.
Effective cybersecurity extends beyond vulnerability management alone. It includes secure-by-design development practices, risk assessment, vulnerability handling and a clear understanding of the software components that make up a system.
As software supply chains grow in complexity and regulatory expectations continue to evolve, organisations need greater visibility into the components they rely on. Traceability, Software Bills of Materials (SBOMs), component transparency and clear development practices help teams assess risk, respond more effectively to vulnerabilities and make informed security decisions.
This visibility is especially important for foundational software components such as the Real Time Operating System (RTOS).
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What is RTOS security?
RTOS security refers to the processes, controls and engineering practices used to protect an RTOS and the applications that depend on it from cybersecurity threats.
Effective RTOS security considers how the software is designed, developed, tested and maintained through secure software development practices. It also considers how the RTOS contributes to the wider security architecture of a system through capabilities such as isolation, resource controls, privilege separation and threat containment.
This can include:
- Threat analysis and risk assessment (TARA)
- Security requirements and risk analysis
- Secure design and coding
- Security testing and verification
- Security and software requirement traceability
- Vulnerability management
- Ongoing maintenance and support
The objective is to understand how security has been addressed, how vulnerabilities are managed and how the RTOS helps support secure-by-design embedded systems.
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Foundational software
Foundational software includes components such as an RTOS and middleware that support the applications running above them.
Because these components play a critical role within a system, organisations often look for strong assurance evidence, rigorous development processes and independent verification when selecting them for safety-critical applications.
Does an RTOS need to be connected to the internet to be a security risk?
No. An RTOS may have no direct network interface or cloud connection but it is still an important part of a product’s security architecture.
The RTOS provides the foundation on which the connected application software runs. It manages resources and system services that other software depends on. If that foundational software contains a vulnerability, the potential impact can extend into the wider system.
This is particularly important when the same RTOS is reused across multiple products. A vulnerability in a widely deployed component can affect every product that incorporates it.
Common RTOS security considerations
RTOS security needs to be considered in the context of the complete embedded system. Depending on the architecture and application, this can include:
Memory protection
Memory corruption and invalid memory access can create security vulnerabilities and affect system behaviour.
Privilege and resource access
Software should only have access to the system resources and services it requires.
Interfaces and communications
APIs, communication paths and external interfaces need to be considered as potential routes into the system.
Third-party software
Libraries, middleware and other software components can introduce vulnerabilities into the product supply chain.
Secure boot and software updates
Products may need mechanisms to establish trust during start-up and securely manage software throughout the product lifecycle.
These considerations cannot be separated completely from the wider application architecture. The RTOS is one layer of the overall security model.
RTOS security and the EU Cyber Resilience Act
The EU Cyber Resilience Act (CRA) introduces cybersecurity requirements for products with digital elements, including requirements covering secure development, vulnerability handling, security updates and documentation.
For manufacturers and software suppliers, this means cybersecurity needs to be considered throughout the product lifecycle.
An RTOS can form part of a product with digital elements. Information about its development, verification, vulnerabilities and maintenance may contribute to the manufacturer’s overall cybersecurity activities.
The exact CRA obligations depend on the product and the organisation’s role in the supply chain. An RTOS does not, by itself, make a complete product compliant with the CRA. However, having appropriate software assurance evidence can help manufacturers build and demonstrate their own compliance.
Why security evidence matters
Security claims are difficult to assess without supporting evidence.
Customers, procurement teams and auditors may want to understand how an embedded software component was developed, tested and maintained. They may also need evidence that requirements have been addressed and that the software can be traced back to its verification activities.
This makes software assurance an important part of RTOS security.
For safety-critical embedded systems, evidence can include, but is not limited to, risk and hazard analysis, verification and validation results and maintenance processes.
The ability to provide this information gives engineering teams greater visibility into the software they are integrating.
Top five RTOS security best practices
Together, these CIA(AG) principles provide a practical foundation for securing RTOS-based embedded systems:
Confidentiality
Ensure information is only accessible to authorised users and that systems expose only the minimum data required for a given task.
Integrity
Protect software, communications and data from unauthorised modification, corruption or tampering throughout the system lifecycle.
Availability
Maintain reliable operation of critical services, resources and communications so the system can perform its intended function when needed.
Authenticity
Verify that users, devices and systems are genuinely who they claim to be before access is granted or trusted communications are established.
Governance
Implement policies, processes and access controls that clearly define responsibilities and ensure appropriate separation between user and administrator privileges.
RTOS security: frequently asked questions
How do you secure an RTOS?
RTOS security should be considered throughout the software lifecycle. Typical activities include security requirements, risk analysis, secure design, secure development, code review, security testing, verification and vulnerability management.
What is the relationship between RTOS security and the CRA?
The CRA introduces cybersecurity requirements for products with digital elements. Where an RTOS forms part of such a product, information about its development, vulnerabilities, security practices and maintenance may contribute to the manufacturer’s cybersecurity and compliance activities.
How are RTOS vulnerabilities managed throughout the software lifecycle?
Vulnerability management does not end when an RTOS is released. Suppliers should have processes for reporting, assessing, tracking and communicating security-relevant issues throughout the supported lifetime of the product.
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