CVE-2025-55018 is a vulnerability in Fortinet FortiOS versions 6.4.3 through 7.6.0 that arises from inconsistent interpretation of HTTP requests, commonly known as HTTP request smuggling. This flaw allows an unauthenticated attacker to craft malicious HTTP headers that can bypass firewall policies by smuggling unlogged HTTP requests through the FortiOS firewall. The vulnerability enables execution of unauthorized commands or code on the affected device, potentially compromising the integrity of the firewall's operation. The attack vector requires no authentication or user interaction, increasing the risk of exploitation. The CVSS 3.1 score is 5.2 (medium), reflecting that while confidentiality is not impacted, integrity can be compromised, and availability remains unaffected. The vulnerability affects multiple major FortiOS versions, including 6.4.3 through 7.6.0, which are widely deployed in enterprise and critical infrastructure environments globally. No public exploits have been reported yet, but the nature of HTTP request smuggling and the critical role of FortiOS in network security make this a significant concern. The vulnerability could allow attackers to evade firewall rules, inject malicious commands, and potentially gain further access within the network. Fortinet has not yet published patches or mitigation details, so organizations must monitor for updates and apply them promptly once available.

For European organizations, this vulnerability poses a risk primarily to network security and integrity. FortiOS devices are commonly used as firewalls and security gateways protecting sensitive data and critical infrastructure. Successful exploitation could allow attackers to bypass firewall policies undetected, execute unauthorized commands, and potentially manipulate network traffic or security controls. This could lead to lateral movement within networks, disruption of security monitoring, or preparation for further attacks. While confidentiality is not directly impacted, the integrity of network defenses is at risk, which can indirectly lead to data breaches or service disruptions. Critical sectors such as finance, energy, telecommunications, and government agencies in Europe rely heavily on Fortinet products, increasing the potential impact. The absence of authentication and user interaction requirements lowers the barrier for attackers, making the threat more accessible. The medium severity rating suggests a moderate but actionable risk that requires timely mitigation to prevent exploitation.

1. Monitor Fortinet's official channels closely for patch releases addressing CVE-2025-55018 and apply updates immediately upon availability. 2. In the interim, implement strict HTTP traffic inspection and anomaly detection to identify and block suspicious HTTP headers indicative of request smuggling attempts. 3. Employ Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) capable of detecting and mitigating HTTP request smuggling techniques. 4. Review and tighten firewall policies to minimize exposure, including restricting HTTP traffic to only necessary sources and destinations. 5. Conduct internal network segmentation to limit the impact of any potential compromise of FortiOS devices. 6. Increase logging and monitoring of FortiOS devices for unusual command execution or policy bypass events. 7. Educate network security teams about HTTP request smuggling and signs of exploitation to improve detection and response capabilities. 8. Consider temporary deployment of additional perimeter security controls to compensate for the vulnerability until patches are applied.