CVE-2025-67779 is a vulnerability in Meta's react-server-dom-parcel package, specifically affecting versions 19.0.2, 19.1.3, and 19.2.2. The issue stems from unsafe deserialization of untrusted payloads received via HTTP requests to Server Function endpoints in React Server Components. Deserialization is a process where data is converted from a format suitable for transmission or storage back into an executable object. When untrusted data is deserialized without proper validation, it can lead to security issues such as code injection or resource exhaustion. In this case, the vulnerability allows an attacker to craft malicious payloads that cause an infinite loop during deserialization, resulting in uncontrolled resource consumption (CWE-400) and denial of service (DoS). This vulnerability is a regression from a previous fix (CVE-2025-55184) that was intended to address similar issues but was incomplete. The flaw does not impact confidentiality or integrity but severely affects availability by hanging the server process and blocking future HTTP requests. The CVSS v3.1 score is 7.5 (high severity), reflecting network attack vector, low attack complexity, no privileges or user interaction required, and a significant impact on availability. No public exploits have been reported yet, but the vulnerability poses a serious risk to applications relying on the affected React Server Components versions. The lack of patch links indicates that a fix may still be pending or in development. Organizations using these versions should consider immediate mitigation steps to prevent exploitation.

For European organizations, the primary impact is denial of service against web applications using the affected react-server-dom-parcel versions. This can lead to service outages, degraded user experience, and potential loss of business continuity, especially for customer-facing or critical internal applications built with React Server Components. The vulnerability does not expose sensitive data or allow code execution beyond resource exhaustion, but the resulting downtime can disrupt operations and damage reputation. Industries with high reliance on web services, such as finance, e-commerce, public sector, and telecommunications, are particularly vulnerable. Additionally, the attack requires no authentication or user interaction, increasing the risk of automated exploitation attempts. Organizations with cloud-hosted or containerized React applications may experience cascading effects if the server process hangs, affecting scalability and availability of dependent services. The absence of known exploits provides a window for proactive mitigation, but the high severity score and ease of exploitation necessitate urgent attention.

1. Monitor Meta's official channels for patches or updates addressing CVE-2025-67779 and apply them promptly once available. 2. Until patches are released, implement strict input validation and sanitization on all Server Function endpoints to reject malformed or suspicious payloads. 3. Employ rate limiting and request throttling on HTTP endpoints to reduce the risk of resource exhaustion from repeated malicious requests. 4. Use Web Application Firewalls (WAFs) with custom rules to detect and block anomalous deserialization payloads targeting React Server Components. 5. Isolate React Server Components in separate processes or containers with resource limits (CPU, memory) to contain potential DoS impact. 6. Conduct code audits and review deserialization logic to identify and harden unsafe deserialization patterns. 7. Implement robust monitoring and alerting for unusual server process hangs or high resource consumption indicative of exploitation attempts. 8. Educate development teams about secure deserialization practices and the risks of unsafe payload handling. 9. Consider temporary disabling or restricting access to Server Function endpoints if feasible until a fix is deployed. 10. Maintain an incident response plan to quickly address potential service disruptions caused by exploitation.