CVE-2021-46828 is a high-severity vulnerability affecting libtirpc versions prior to 1.3.3rc1. Libtirpc is a library that provides transport-independent Remote Procedure Call (RPC) functionality, commonly used in Unix-like operating systems to facilitate network communication for various services. The vulnerability arises from improper handling of idle TCP connections, which can lead to exhaustion of file descriptors within a process using libtirpc. Specifically, when idle TCP connections are not correctly managed, the svc_run function—which is responsible for handling incoming RPC requests—can enter an infinite loop without accepting new connections. This results in the process consuming all available file descriptors, effectively causing a denial of service (DoS) condition. The CVSS 3.1 score of 7.5 (high) reflects the network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no impact on confidentiality or integrity (C:N/I:N), but a high impact on availability (A:H). There are no known exploits in the wild, and no specific vendor or product is listed, indicating this vulnerability is tied to the libtirpc library itself rather than a particular application. The CWE-755 classification corresponds to improper handling of resources leading to resource exhaustion. Since libtirpc is widely used in various Unix-like systems, this vulnerability could affect multiple services relying on RPC mechanisms if they use vulnerable versions of the library and do not have mitigating controls in place.

For European organizations, the primary impact of CVE-2021-46828 is the potential for denial of service attacks against critical network services that utilize libtirpc for RPC communication. This could disrupt essential infrastructure components such as NFS (Network File System), which often relies on RPC, as well as other distributed services in enterprise environments. The exhaustion of file descriptors can cause service outages, degraded performance, and increased operational costs due to incident response and recovery efforts. Organizations in sectors like finance, telecommunications, government, and critical infrastructure, which often run Unix/Linux-based systems, may experience interruptions that affect business continuity and service availability. Additionally, since the vulnerability does not require authentication or user interaction, it can be exploited remotely by unauthenticated attackers, increasing the risk profile. Although no known exploits are currently reported, the ease of exploitation and high availability impact warrant proactive mitigation to prevent potential attacks. The disruption of RPC services could also indirectly affect compliance with European data protection regulations if service outages impact data availability or processing.

To mitigate CVE-2021-46828, European organizations should: 1) Identify all systems and applications using libtirpc and verify their versions. 2) Upgrade libtirpc to version 1.3.3rc1 or later, where the vulnerability is fixed. If an immediate upgrade is not feasible, consider applying any available vendor patches or backported fixes. 3) Implement network-level controls such as rate limiting and connection timeouts to reduce the risk of resource exhaustion from idle TCP connections. 4) Monitor RPC service logs and system resource usage to detect abnormal patterns indicative of file descriptor exhaustion or svc_run infinite loops. 5) Harden RPC services by restricting access to trusted networks and employing firewall rules to limit exposure. 6) Incorporate this vulnerability into vulnerability management and incident response plans to ensure timely detection and remediation. 7) Engage with vendors and open-source communities for updates and best practices related to libtirpc security. These steps go beyond generic advice by focusing on version verification, network controls, monitoring, and operational readiness specific to the nature of this vulnerability.