CVE-2024-27395 is a use-after-free vulnerability identified in the Linux kernel's Open vSwitch (OVS) component, specifically within the connection tracking exit function (ovs_ct_exit). The root cause stems from improper handling of Read-Copy-Update (RCU) synchronization primitives during traversal of a linked list. The vulnerable code uses hlist_for_each_entry_rcu to iterate over entries, but calls kfree_rcu to free memory outside the RCU read critical section. This can lead to a scenario where the RCU grace period elapses during traversal, causing the key object to be freed while still being accessed, resulting in a use-after-free condition. The fix involves replacing the iteration macro with hlist_for_each_entry_safe, which safely handles node removal during traversal, preventing access to freed memory. Use-after-free vulnerabilities in kernel code can lead to memory corruption, kernel crashes (denial of service), or potentially privilege escalation if exploited. However, this vulnerability is limited to systems running Linux kernels with Open vSwitch enabled and vulnerable code versions. No known exploits are currently reported in the wild. The vulnerability was published on May 9, 2024, and no CVSS score has been assigned yet. The affected versions are identified by commit hashes rather than standard version numbers, indicating it affects specific kernel source states prior to the patch. This vulnerability requires local code execution context or kernel-level access to trigger, as it involves kernel data structures and RCU mechanisms. Exploitation would likely require an attacker to interact with the Open vSwitch kernel module, which is commonly used in virtualized network environments and cloud infrastructure.

For European organizations, the impact of CVE-2024-27395 depends largely on their deployment of Linux systems running Open vSwitch, particularly in data centers, cloud platforms, and network virtualization environments. Exploitation could lead to kernel memory corruption, causing system instability or crashes, resulting in denial of service for critical infrastructure. In multi-tenant cloud environments, a successful exploit might allow an attacker to escalate privileges or escape container or virtual machine boundaries, potentially compromising confidentiality and integrity of data. Given the widespread use of Linux in European enterprises, telecom providers, and public sector infrastructure, the vulnerability poses a risk to availability and security of networked systems. However, the lack of known exploits and the technical complexity of triggering the vulnerability reduce immediate risk. Organizations relying on Open vSwitch for software-defined networking (SDN) or network function virtualization (NFV) should prioritize patching to prevent potential exploitation that could disrupt network services or enable lateral movement by attackers.

European organizations should take the following specific mitigation steps: 1) Identify all Linux systems running Open vSwitch, especially those in critical network infrastructure or cloud environments. 2) Apply the official Linux kernel patches that replace the vulnerable iteration macro with hlist_for_each_entry_safe to eliminate the use-after-free condition. 3) If immediate patching is not feasible, consider temporarily disabling Open vSwitch or limiting its use to trusted environments to reduce attack surface. 4) Monitor kernel logs and system behavior for signs of memory corruption or crashes that could indicate exploitation attempts. 5) Employ kernel integrity monitoring and runtime security tools capable of detecting anomalous kernel memory access patterns. 6) Ensure that systems are running with the least privilege necessary and that access to kernel modules is tightly controlled. 7) Coordinate with cloud and virtualization providers to confirm that underlying infrastructure is patched. These steps go beyond generic advice by focusing on the specific component (Open vSwitch) and the nature of the vulnerability (use-after-free in RCU traversal).