Aircraft Collision Avoidance Systems Hit by High-Severity ICS Vulnerability 

Overview 

A pair of vulnerabilities in the Traffic Alert and Collision Avoidance System (TCAS) II for avoiding midair collisions were among 20 vulnerabilities reported by Cyble in its weekly Industrial Control System (ICS) Vulnerability Intelligence Report. 

The midair collision system flaws have been judged at low risk of being exploited, but one of the vulnerabilities does not presently have a fix. They could potentially be exploited from adjacent networks. 

Other ICS vulnerabilities covered in the January 15-21 Cyble report to subscribers include flaws in critical manufacturing, energy and other critical infrastructure systems. The full report is available for subscribers, but Cyble is publishing information on the TCAS vulnerabilities in the public interest. 

TCAS II Vulnerabilities 

The TCAS II vulnerabilities were reported to the U.S. Cybersecurity and Infrastructure Security Agency (CISA) by European researchers and defense agencies. CISA in turn disclosed the vulnerabilities in a January 21 advisory. 

The vulnerabilities are still undergoing analysis by NIST, but Cyble vulnerability researchers said the weaknesses “underscore the urgent need for enhanced input validation and secure configuration controls in transportation systems.” 

TCAS airborne devices function independently of ground-based air traffic control (ATC) systems, according to the FAA, and provide collision avoidance protection for a range of aircraft types. TCAS II is a more advanced system for commercial aircraft with more than 30 seats or a maximum takeoff weight of more than 33,000 pounds. TCAS II offers advanced features such as recommended escape maneuvers for avoiding midair collisions. 

The first vulnerability, CVE-2024-9310, is an “Untrusted Inputs” vulnerability in TCAS II that presently carries a CVSS 3.1 base score of 6.1. 

CISA notes that “By utilizing software-defined radios and a custom low-latency processing pipeline, RF signals with spoofed location data can be transmitted to aircraft targets. This can lead to the appearance of fake aircraft on displays and potentially trigger undesired Resolution Advisories (RAs).” 

The second flaw, CVE-2024-11166, is an 8.2-severity External Control of System or Configuration Setting vulnerability. TCAS II systems using transponders compliant with MOPS earlier than RTCA DO-181F could be attacked by threat actors impersonating a ground station to issue a Comm-A Identity Request, which can set the Sensitivity Level Control (SLC) to the lowest setting and disable the Resolution Advisory (RA), leading to a denial-of-service condition. 

“After consulting with the Federal Aviation Administration (FAA) and the researchers regarding these vulnerabilities, it has been concluded that CVE-2024-11166 can be fully mitigated by upgrading to ACAS X or by upgrading the associated transponder to comply with RTCA DO-181F,” CISA said, adding that there is currently no mitigation available for CVE-2024-9310. 

CISA said the vulnerabilities in the TCAS II standard were exploited in a lab environment. 

“However, they require very specific conditions to be met and are unlikely to be exploited outside of a lab setting,” the agency said. “Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.” 

No known publicly available exploit targeting the vulnerabilities has been reported at this time. 

Recommendations for Mitigating ICS Vulnerabilities  

The full Cyble report recommended a number of controls for mitigating ICS vulnerabilities and improving the overall security of ICS systems. The measures include: 

1. Staying on top of security advisories and patch alerts issued by vendors and regulatory bodies like CISA. A risk-based approach to vulnerability management is recommended, with the goal of reducing the risk of exploitation. 

2. Implementing a Zero-Trust Policy to minimize exposure and ensuring that all internal and external network traffic is scrutinized and validated. 

3. Developing a comprehensive patch management strategy that covers inventory management, patch assessment, testing, deployment, and verification. Automating these processes can help maintain consistency and improve efficiency. 

4. Proper network segmentation can limit the potential damage caused by an attacker and prevent lateral movement across networks. This is particularly important for securing critical ICS assets. 

5. Conducting regular vulnerability assessments and penetration testing to identify gaps in security that might be exploited by threat actors. 

6. Establishing and maintaining an incident response plan, and ensuring that the plan is tested and updated regularly to adapt to the latest threats. 

7. Ongoing cybersecurity training programs should be mandatory for all employees, especially those working with Operational Technology (OT) systems. Training should focus on recognizing phishing attempts, following authentication procedures, and understanding the importance of cybersecurity practices in day-to-day operations. 

Conclusion 

The TCAS II flaws and other ICS vulnerabilities show the danger that vulnerabilities in critical infrastructure environments can pose, with the potential to disrupt operations, compromise sensitive data, and cause physical damage with potentially tragic outcomes. Staying on top of ICS vulnerabilities and applying good cybersecurity hygiene and controls can limit risk. 

To access the full report on ICS vulnerabilities observed by Cyble, along with additional insights and details, click here. By adopting a comprehensive, multi-layered security approach that includes effective vulnerability management, timely patching, and ongoing employee training, organizations can reduce their exposure to cyber threats. With the right tools and intelligence, such as those offered by Cyble, critical infrastructure can be better protected, ensuring its resilience and security in an increasingly complex cyber landscape. 

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