CVE-2024-56642 is a high-severity use-after-free vulnerability in the Linux kernel's Transparent Inter-Process Communication (TIPC) subsystem, specifically affecting the UDP kernel socket cleanup process within the cleanup_bearer() function. The flaw arises due to improper synchronization in the cleanup sequence of UDP kernel sockets when bearer_disable() triggers tipc_udp_disable(). The cleanup is deferred via a workqueue that calls cleanup_bearer(). However, the decrement of the workqueue count (wq_count) occurs prematurely before the kernel socket is fully released. This premature decrement allows cleanup_net() to proceed while the socket is still in use, leading to a use-after-free condition. This vulnerability was identified through syzkaller fuzz testing and confirmed by Kernel Memory Sanitizer (KMSAN) reports, which detected use-after-free errors in udp_hashslot and related UDP socket release functions. The root cause is a race condition in the workqueue handling and socket release order, which can cause kernel memory corruption. Exploitation of this flaw could allow a local attacker with limited privileges (PR:L) to execute arbitrary code or cause denial of service by crashing the kernel, impacting confidentiality, integrity, and availability. The vulnerability affects multiple recent Linux kernel versions as identified by specific commit hashes. The CVSS v3.1 score is 7.8 (high), reflecting the local attack vector, low attack complexity, required privileges, no user interaction, and high impact on confidentiality, integrity, and availability. No known exploits are currently reported in the wild, but the nature of the flaw and its kernel-level impact make it a significant risk once weaponized. The fix involves reordering the decrement of the workqueue count to occur after the socket release, ensuring proper synchronization and preventing use-after-free conditions.

For European organizations, this vulnerability poses a critical risk to any systems running vulnerable Linux kernel versions, especially servers and infrastructure handling network communications using TIPC and UDP sockets. Exploitation could lead to kernel crashes (denial of service), unauthorized code execution with kernel privileges, or data leakage, severely impacting system availability and security. This is particularly concerning for critical infrastructure providers, cloud service operators, telecom companies, and enterprises relying on Linux-based networking stacks. The vulnerability's local attack vector means that attackers need some level of access, but given the prevalence of multi-tenant environments and containerized deployments in Europe, lateral movement could enable exploitation. The high impact on confidentiality, integrity, and availability could disrupt business operations, cause data breaches, and undermine trust in IT services. Additionally, the vulnerability could be leveraged in targeted attacks against strategic sectors such as finance, energy, and government institutions across Europe, where Linux is widely deployed.

European organizations should prioritize patching affected Linux kernel versions as soon as vendor updates become available, ensuring the fix that reorders the workqueue decrement is applied. In environments where immediate patching is not feasible, organizations should restrict local access to systems running vulnerable kernels by enforcing strict access controls, using hardened container runtimes, and employing kernel lockdown features where possible. Monitoring kernel logs and system behavior for signs of use-after-free exploitation attempts or unusual workqueue activity can aid early detection. Employing kernel runtime security tools such as eBPF-based monitors or KRSI (Kernel Runtime Security Instrumentation) can help detect anomalous kernel memory operations. Organizations should also review and limit the use of TIPC where not necessary, as this subsystem is the attack surface. Finally, maintaining up-to-date intrusion detection and prevention systems that can identify exploitation attempts targeting kernel vulnerabilities is recommended.