Top Highlights
- The Shadowserver Foundation warns that over 2,000 FortiClient EMS instances worldwide are publicly accessible, with two confirmed active exploitations of critical unauthenticated remote code execution vulnerabilities.
- The vulnerabilities, CVE-2026-35616 (newly disclosed) and CVE-2026-21643, allow remote attackers to fully control affected systems without credentials, posing severe security risks.
- Affected regions include the U.S. and Germany, where compromised EMS servers could enable attackers to manipulate endpoints, extract VPN credentials, and establish persistent access.
- Immediate mitigation steps include applying available patches, restricting internet-facing access, monitoring logs, and enabling threat detection to prevent exploitation.
Underlying Problem
The Shadowserver Foundation has issued an urgent warning about a serious security threat affecting FortiClient Enterprise Management Server (EMS) systems globally. Over 2,000 instances are publicly accessible, and two critical vulnerabilities—CVE-2026-35616 and CVE-2026-21643—have been exploited in real-world attacks. Both are unauthenticated remote code execution flaws, meaning attackers can remotely control vulnerable servers without needing credentials. This exploitation risks severe consequences, such as tampering with endpoint configurations, stealing VPN credentials, or deploying malicious policies, thus giving hackers persistent access to entire networks.
The attack’s scope is widespread, impacting mainly the United States and Germany. Threat actors are actively exploiting these flaws, exploiting unpatched systems to gain control over large organizations’ endpoints. The report, provided by Shadowserver, highlights the urgent need for organizations to apply patches, restrict internet-facing access, review logs for suspicious activity, and enhance threat monitoring. Fortinet has emphasized immediate firmware updates and advised additional security measures to prevent further compromise. This incident underscores the increasing targeting of Fortinet products by malicious groups seeking initial access into enterprise environments.
Potential Risks
The widespread exposure of over 2,000 FortiClient EMS instances online, combined with active remote code execution (RCE) vulnerabilities being exploited in the wild, poses a serious threat to businesses. If your organization relies on FortiClient EMS for managing security, attackers can gain unauthorized access, leading to data breaches or system disruptions. Consequently, this can result in financial losses, legal penalties, and damage to your reputation. Moreover, the exploitation may cause operational downtime, hurting productivity and customer trust. Therefore, without prompt action, your business risks severe security incidents that could significantly impair your overall stability and growth.
Possible Action Plan
In today’s rapidly evolving cybersecurity landscape, swift and effective remediation is crucial to preventing widespread damage and safeguarding sensitive information when vulnerabilities are exploited in the wild.
Mitigation Strategies
- Immediate Patch Deployment: Apply the latest firmware and software updates to all FortiClient EMS instances to close known vulnerabilities.
- Network Segmentation: Isolate affected systems from critical networks to limit the potential for lateral movement and reduce attack surface exposure.
- Access Controls: Enforce least privilege principles, ensuring only authorized personnel have access to management interfaces and sensitive data.
- Enhanced Monitoring: Deploy continuous monitoring tools to detect unusual activity and potential exploitation attempts rapidly.
- Vulnerability Scanning: Conduct comprehensive scans across all EMS instances to identify additional weaknesses or signs of compromise.
- Incident Response Preparedness: Activate or refine existing incident response plans to ensure quick action in containment, eradication, and recovery efforts.
- User Training and Awareness: Educate administrators and users on recognizing signs of malicious activity and best practices for security.
- Vendor Coordination: Communicate promptly with Fortinet for guidance, patches, and updates related to the vulnerability.
- Documentation and Reporting: Maintain detailed records of the incident, response actions, and communications for accountability and future improvement.
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Disclaimer: The information provided may not always be accurate or up to date. Please do your own research, as the cybersecurity landscape evolves rapidly. Intended for secondary references purposes only.
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