CVE-2025-41243 is a critical vulnerability affecting Spring Cloud Gateway Server Webflux, a component widely used for building API gateways in microservice architectures. The vulnerability stems from improper neutralization of special elements used in Expression Language (EL) statements, classified under CWE-917 (Improper Neutralization of Special Elements used in an Expression Language Statement) and CWE-94 (Improper Control of Generation of Code). Specifically, this flaw allows attackers to manipulate Spring Environment properties via the actuator web endpoints exposed by Spring Cloud Gateway Server Webflux. The vulnerability requires that the application uses Spring Cloud Gateway Server Webflux (not WebMVC), has Spring Boot actuator as a dependency, and that the actuator endpoints are enabled and exposed (management.endpoints.web.exposure.include=gateway) without proper security controls. When these conditions are met, unauthenticated remote attackers can exploit the EL injection to execute arbitrary code or commands, leading to full compromise of the affected system. The CVSS v3.1 base score is 10.0, indicating a critical severity with network attack vector, no required privileges or user interaction, and complete impact on confidentiality, integrity, and availability. Although no public exploits are currently known in the wild, the ease of exploitation and the critical impact make this vulnerability a high priority for remediation. Affected versions include Spring Cloud Gateway 3.1.x, 4.0.x, 4.1.x, 4.2.x, and 4.3.x.

For European organizations, this vulnerability poses a severe risk, especially for enterprises relying on Spring Cloud Gateway Server Webflux to manage internal and external API traffic. Exploitation can lead to unauthorized access, data breaches involving sensitive personal and business data, service disruption, and potential lateral movement within corporate networks. Given the criticality of the CVSS score and the fact that no authentication is required, attackers can remotely compromise systems, potentially impacting compliance with GDPR and other data protection regulations. The disruption of API gateways could also affect critical business operations, including financial transactions, supply chain communications, and customer-facing services. The risk is amplified in sectors such as finance, healthcare, telecommunications, and government services, where Spring Cloud Gateway is commonly deployed and where data sensitivity and service availability are paramount.

Organizations should immediately audit their Spring Cloud Gateway Server Webflux deployments to identify if the actuator endpoints are enabled and exposed without proper security controls. Specifically, verify the 'management.endpoints.web.exposure.include' property and restrict or disable the 'gateway' actuator endpoint if not strictly necessary. Implement strong authentication and authorization mechanisms on all actuator endpoints, preferably integrating with enterprise identity providers and enforcing least privilege access. Upgrade affected Spring Cloud Gateway versions to patched releases once available from the vendor. In the interim, consider network-level protections such as firewall rules or API gateway policies to restrict access to actuator endpoints to trusted internal IPs only. Additionally, monitor logs and network traffic for unusual access patterns targeting actuator endpoints. Employ runtime application self-protection (RASP) or web application firewalls (WAF) with EL injection detection capabilities as an additional layer of defense.