CVE-2023-52839 is a vulnerability identified in the Linux kernel, specifically within the performance monitoring (perf) subsystem related to the handling of CPU counters on RISC-V architectures. The issue arises from an incorrect implementation in the perf driver where a broadcast to other CPUs is performed when starting a performance counter, which is unnecessary and leads to kernel warnings and potential instability. The root cause is tied to a previous fix (commit 3fec323339a4) intended to address a panic in RISC-V SBI mmap support; however, this fix mistakenly included broadcasting to other CPUs when starting counters, which should only occur during mmap operations where counters might already be active on other CPUs. The vulnerability manifests as kernel warnings and stack traces indicating improper CPU intercommunication during perf event handling, specifically in the smp_call_function_many_cond function. Although no direct exploit has been reported, the flaw could cause kernel instability or denial of service (DoS) conditions on affected systems running vulnerable Linux kernel versions. The vulnerability affects Linux kernels incorporating the faulty commit and is particularly relevant to RISC-V platforms using the perf subsystem for performance monitoring. The fix involves removing the unnecessary broadcast to other CPUs when starting counters, thereby preventing the kernel warnings and potential instability.

For European organizations, the impact of CVE-2023-52839 primarily concerns systems running Linux kernels with the affected commit, especially those utilizing RISC-V architectures. While RISC-V adoption in Europe is still emerging, sectors investing in advanced computing, embedded systems, and research may deploy such platforms. The vulnerability could lead to kernel warnings and potential system instability or crashes when performance monitoring tools are used, impacting system availability and reliability. This is particularly critical for high-availability environments, industrial control systems, or research institutions relying on precise performance metrics. Although no direct exploitation is known, the potential for denial of service through kernel panics or degraded system performance could disrupt operations. Confidentiality and integrity impacts appear minimal since the vulnerability does not directly enable privilege escalation or data leakage. However, availability degradation could indirectly affect business continuity and operational efficiency.

European organizations should take the following specific mitigation steps: 1) Identify Linux systems running kernels with the affected commit (3fec323339a4) or versions derived from it, focusing on RISC-V platforms. 2) Apply the official Linux kernel patches that remove the unnecessary CPU broadcast when starting performance counters; monitor Linux kernel mailing lists and vendor advisories for updated stable releases incorporating this fix. 3) If immediate patching is not feasible, limit or avoid the use of perf record commands with multiple event counters on affected systems to reduce triggering the vulnerability. 4) Implement robust kernel crash monitoring and alerting to detect any instability related to perf subsystem usage. 5) For embedded or specialized RISC-V devices, coordinate with hardware and OS vendors to ensure timely firmware and kernel updates. 6) Incorporate this vulnerability into vulnerability management and patching workflows, prioritizing systems where performance monitoring is critical. 7) Conduct testing in controlled environments before deploying patched kernels to production to ensure stability and compatibility.