CVE-2023-52615 is a vulnerability identified in the Linux kernel's hardware random number generator (hwrng) core subsystem. The flaw arises from a deadlock condition triggered during concurrent access patterns involving the /dev/hwrng device. Specifically, when a user process reads from /dev/hwrng into memory that has also been memory-mapped (mmap-ed) from /dev/hwrng, a page fault occurs. This page fault leads to a recursive read operation on the hwrng device, which in turn causes a deadlock situation within the kernel. The root cause is the handling of the copy_to_user operation, which previously did not use a stack buffer, allowing the recursive read and deadlock to manifest. The vulnerability was addressed by modifying the kernel code to use a stack buffer during the copy_to_user call, thereby preventing the recursive read and eliminating the deadlock. This issue affects multiple versions of the Linux kernel as indicated by the repeated commit hash references, and it was publicly disclosed in March 2024. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2023-52615 primarily concerns system availability and stability. The deadlock in the kernel's hwrng subsystem can cause processes that interact with /dev/hwrng to hang indefinitely, potentially leading to system freezes or degraded performance. Systems relying on hardware random number generation for cryptographic operations or security services may experience interruptions or delays, which could cascade into broader service disruptions. Although this vulnerability does not directly expose confidentiality or integrity risks, denial of service conditions in critical infrastructure, financial services, or governmental systems could have significant operational consequences. Given the widespread use of Linux in servers, cloud environments, and embedded devices across Europe, unpatched systems remain at risk of encountering these deadlocks, especially under workloads or applications that utilize /dev/hwrng with mmap and read operations concurrently.

European organizations should prioritize updating their Linux kernel to the patched versions that include the fix for CVE-2023-52615. Since the vulnerability involves kernel-level code, applying official kernel updates from trusted Linux distributions is the most effective mitigation. Organizations should audit their systems to identify any applications or services that perform concurrent mmap and read operations on /dev/hwrng and consider temporarily disabling or restricting such usage until patches are applied. Additionally, monitoring system logs and kernel messages for signs of deadlocks or hangs related to /dev/hwrng can help detect attempts to trigger this issue. For environments where immediate patching is not feasible, implementing kernel-level resource limits or isolating affected workloads in containers or virtual machines may reduce the risk of widespread impact. Finally, maintaining robust backup and recovery procedures will help mitigate operational disruptions caused by potential deadlocks.