CVE-2025-55182 is a critical vulnerability affecting Meta's React Server Components, specifically versions 19.0.0, 19.1.0, and 19.2.0, including the react-server-dom-parcel, react-server-dom-turbopack, and react-server-dom-webpack packages. The root cause is unsafe deserialization of untrusted data within HTTP requests directed at Server Function endpoints. Deserialization vulnerabilities occur when untrusted input is parsed into executable code or objects without proper validation or sanitization, enabling attackers to craft malicious payloads that execute arbitrary code on the server. This vulnerability requires no authentication or user interaction, making it remotely exploitable over the network. The CVSS v3.1 score of 10 reflects the highest severity, indicating that exploitation can lead to complete compromise of confidentiality, integrity, and availability of affected systems. The vulnerability is particularly dangerous in server-side React components because it undermines the trust boundary between client input and server execution. Although no active exploits have been reported, the simplicity of exploitation and the widespread use of React Server Components in modern web applications necessitate urgent remediation. The lack of available patches at the time of disclosure increases the risk window, requiring organizations to implement interim mitigations. This vulnerability highlights the critical importance of secure deserialization practices and input validation in server-side JavaScript frameworks.

For European organizations, the impact of CVE-2025-55182 is substantial. Organizations relying on Meta's React Server Components for server-side rendering or server functions in web applications face the risk of remote code execution, which can lead to full system compromise, data breaches, and service disruption. Confidentiality is at risk as attackers can access sensitive data processed or stored by the affected applications. Integrity is compromised since attackers can alter application behavior or data. Availability can be affected through denial-of-service conditions or destruction of critical resources. The vulnerability's remote and unauthenticated nature increases the attack surface, especially for public-facing web services. This can affect sectors such as finance, healthcare, government, and e-commerce, where React-based applications are prevalent. Additionally, the potential for lateral movement within networks after initial compromise raises concerns about broader organizational impact. The absence of known exploits currently provides a small window for proactive defense, but the critical severity demands immediate action to prevent exploitation. Failure to address this vulnerability could lead to regulatory consequences under GDPR if personal data is compromised.

Given the absence of patches at disclosure, European organizations should implement the following specific mitigations: 1) Restrict network access to Server Function endpoints by implementing strict firewall rules or network segmentation to limit exposure to trusted sources only. 2) Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious deserialization payloads or anomalous HTTP request patterns targeting Server Function endpoints. 3) Conduct thorough input validation and sanitization on all data received by Server Function endpoints to prevent malicious payloads from being processed. 4) Monitor logs and network traffic for unusual activity indicative of exploitation attempts, including unexpected deserialization operations or code execution traces. 5) If feasible, temporarily disable or isolate the use of vulnerable React Server Components until official patches are released. 6) Engage with Meta's security advisories and apply patches immediately upon availability. 7) Review and update incident response plans to include scenarios involving deserialization attacks and remote code execution. 8) Educate development teams on secure coding practices related to deserialization and server-side component security to prevent future vulnerabilities.