CVE-2025-62409 is a NULL pointer dereference vulnerability classified under CWE-476, affecting the Envoy proxy, a widely used cloud-native edge and service proxy. The issue exists in versions prior to 1.36.1, 1.35.5, 1.34.9, and 1.33.10. The vulnerability manifests when large TCP requests or responses are processed during the closing phase of a connection. Specifically, if upstream data continues to arrive while the connection is closing, the flow control management logic in Envoy triggers a buffer watermark callback that references a NULL pointer, causing the TCP connection pool to crash. This impacts both TCP proxy functionality and mixed HTTP/1 and HTTP/2 use cases that rely on ALPN (Application-Layer Protocol Negotiation). The vulnerability can be triggered remotely without authentication or user interaction, making it accessible to unauthenticated attackers. The consequence is a denial of service (DoS) condition due to crashing connection pools, potentially disrupting network traffic and service availability. The issue has been addressed in the specified patched versions of Envoy. No known exploits have been reported in the wild as of the publication date, but the vulnerability's nature makes it a significant risk for environments relying on vulnerable Envoy versions for critical network proxying and edge services.

For European organizations, the primary impact of CVE-2025-62409 is the risk of denial of service caused by crashing TCP connection pools in Envoy proxies. This can lead to service disruptions, degraded network performance, and potential outages in cloud-native applications, microservices architectures, and edge computing environments that rely on Envoy for traffic management. Organizations operating critical infrastructure, financial services, telecommunications, and cloud service providers are particularly at risk due to their reliance on stable and high-availability network proxies. The vulnerability could be exploited remotely without authentication, increasing the attack surface. Disruptions could affect customer-facing services, internal communications, and inter-service connectivity, potentially causing financial losses and reputational damage. Additionally, the mixed HTTP/1 and HTTP/2 use cases affected mean that a wide range of web services could be impacted. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits in the future.

European organizations should immediately assess their Envoy proxy deployments to identify versions prior to 1.36.1, 1.35.5, 1.34.9, and 1.33.10. Upgrading to these patched versions is the most effective mitigation. Network administrators should implement strict ingress filtering and rate limiting to reduce the likelihood of large, malformed TCP requests triggering the vulnerability. Monitoring Envoy logs and metrics for unusual connection pool crashes or flow control anomalies can provide early detection of exploitation attempts. Employing redundancy and failover mechanisms for Envoy proxies can minimize service disruption if crashes occur. Organizations should also review their ALPN configurations to ensure they are up to date and consider isolating vulnerable proxy instances from critical network segments until patched. Regular vulnerability scanning and patch management processes should be enforced to prevent similar issues. Finally, maintaining an incident response plan for DoS events involving proxy infrastructure is recommended.