CVE-2024-57974 is a vulnerability in the Linux kernel's UDP socket handling mechanism. The issue arises from a race condition between changing a UDP socket's local address via connect() and the subsequent rehashing process that updates internal hash tables used for socket lookup. Specifically, when a UDP socket changes its local address while receiving datagrams, there is a window during which lookup operations fail because the secondary hash (based on port and address) and the four-tuple hash (local and remote ports and addresses) have not yet been updated. This leads to the socket being temporarily unreachable. The vulnerability manifests as a failure to find the socket during this rehashing window, causing the kernel to respond with an ICMP 'port unreachable' message to the sender. This behavior was observed in scenarios involving socat UDP4-LISTEN servers and clients sending datagrams concurrently on different CPU threads. The issue was initially detected during Podman container network namespace tests, where UDP functionality was intermittently failing due to this race condition. The problem is rooted in the introduction of secondary hash chains and rehash operations in recent Linux kernel commits aimed at optimizing UDP bind() and connect() operations. However, the rehash on connect() is incomplete, as it does not prevent socket lookup failures during the rehashing process. The vulnerability does not appear to have known exploits in the wild yet, but it can cause intermittent UDP communication failures and ICMP port unreachable errors, which could disrupt applications relying on UDP socket connections, especially those using connect() to set up directed flows. No CVSS score has been assigned to this vulnerability as of the published date.

For European organizations, the impact of CVE-2024-57974 primarily concerns the reliability and availability of UDP-based network services running on Linux systems. UDP is widely used for various applications including DNS, VoIP, streaming media, gaming, and containerized microservices communication. The race condition causing temporary socket unreachability can lead to intermittent communication failures, degraded service quality, or application errors. In containerized environments, common in European enterprises adopting cloud-native architectures, this vulnerability could cause sporadic network disruptions affecting container networking and orchestration tools like Podman. While the vulnerability does not directly lead to data breaches or privilege escalation, the resulting denial of UDP communication could impact critical infrastructure services, real-time communications, and operational continuity. Organizations relying on UDP for internal or external services may experience increased troubleshooting complexity and potential service-level agreement (SLA) violations. The lack of authentication or user interaction requirements means the issue can occur naturally under normal operational conditions, especially in multi-threaded or multi-CPU environments common in modern servers.

To mitigate the effects of CVE-2024-57974, European organizations should: 1) Apply the latest Linux kernel patches that address this race condition as soon as they become available from trusted Linux distributions or upstream sources. 2) Monitor UDP-based services for signs of intermittent connectivity issues or ICMP port unreachable messages, especially in containerized or multi-threaded environments. 3) Where possible, avoid relying on connect() calls on UDP sockets in high-concurrency scenarios until patched, or implement application-level retries and error handling to gracefully recover from transient failures. 4) Consider isolating critical UDP services on dedicated CPU cores or network namespaces to reduce concurrency-induced race conditions. 5) Employ network monitoring tools capable of detecting abnormal ICMP traffic patterns that may indicate this issue. 6) For containerized deployments, ensure container runtimes and networking plugins are updated to versions that include fixes or workarounds for this vulnerability. 7) Engage with Linux vendor support channels to obtain backported patches if using long-term support kernels. These steps go beyond generic advice by focusing on operational practices and environment-specific configurations to reduce the likelihood and impact of the race condition.