CVE-2022-23606 is a medium-severity vulnerability affecting Envoy, an open-source edge and service proxy widely used in cloud-native application architectures. The vulnerability arises from uncontrolled recursion in the process of disconnecting idle connections when a cluster is deleted via the Cluster Discovery Service (CDS). Specifically, when a cluster is removed, Envoy attempts to disconnect all idle connections associated with that cluster's endpoints. Due to a recursive call in the disconnection logic, if the cluster has a large number of idle connections, the recursion depth can grow excessively, leading to stack exhaustion. This results in abnormal process termination or a crash of the Envoy proxy. The affected versions include Envoy releases from 1.20.0 up to but not including 1.20.2, and from 1.21.0 up to but not including 1.21.1. The vulnerability is categorized under CWE-674 (Uncontrolled Recursion), which indicates a failure to properly limit recursion depth, causing resource exhaustion. No known exploits have been reported in the wild, but the impact is a denial of service (DoS) condition due to process crash. Users are advised to upgrade to patched versions beyond 1.20.2 or 1.21.1 to mitigate this issue. Since Envoy is often deployed as a critical component in service meshes, API gateways, and edge proxies, this vulnerability can disrupt service availability if exploited or triggered unintentionally during cluster management operations.

For European organizations, the primary impact of CVE-2022-23606 is on service availability. Envoy is commonly used in microservices architectures, cloud-native environments, and service mesh implementations, which are prevalent in sectors such as finance, telecommunications, healthcare, and government services across Europe. A crash of Envoy proxies due to this vulnerability could lead to temporary denial of service, disrupting internal and external communications, API traffic, and load balancing functions. This can degrade user experience, interrupt business-critical workflows, and potentially cause cascading failures in dependent systems. While the vulnerability does not directly compromise confidentiality or integrity, the availability impact can be significant, especially for organizations relying on Envoy for high-availability and low-latency services. Additionally, the need to frequently delete and update clusters in dynamic environments (e.g., auto-scaling or continuous deployment pipelines) increases the risk of triggering this issue. The absence of known exploits reduces immediate risk, but the vulnerability remains a concern for operational stability.

To mitigate CVE-2022-23606, European organizations should: 1) Upgrade Envoy to versions 1.20.2 or later, or 1.21.1 or later, where the recursion issue has been fixed. 2) Audit and monitor cluster management operations to minimize unnecessary frequent cluster deletions, especially in environments with large numbers of idle connections. 3) Implement robust health checks and automated restart mechanisms to quickly recover from Envoy crashes, reducing downtime impact. 4) Use connection draining and graceful shutdown procedures to reduce the number of idle connections at cluster removal time. 5) In environments where immediate upgrade is not feasible, consider limiting the number of idle connections per cluster or implementing rate limiting on cluster deletion requests to avoid triggering deep recursion. 6) Continuously monitor Envoy logs and metrics for signs of abnormal process terminations or stack overflow errors. 7) Incorporate this vulnerability into incident response and risk assessment frameworks to prioritize patching and operational controls. These steps go beyond generic advice by focusing on operational practices around cluster lifecycle and connection management specific to Envoy deployments.