CVE-2023-52598 is a vulnerability identified in the Linux kernel specifically affecting the s390 architecture's ptrace interface handling of the floating point control (fpc) register. The ptrace system call allows one process (the tracer) to observe and control the execution of another process (the tracee), commonly used for debugging. In this vulnerability, when the tracer modifies the fpc register of the tracee, the new value is temporarily loaded into the fpc register for validity testing. However, if an interrupt occurs during this temporary loading and floating point or vector registers are used within the interrupt context, the kernel's save_fpu_regs() function mistakenly saves the tracer's floating point/vector registers assuming they belong to user space. Although the test_fp_ctl() function restores the original user-space fpc register value, this restoration is discarded upon returning to user space. Consequently, the tracer process continues execution with the fpc register value intended for the tracee, leading to corruption of the tracer's floating point control state. This can cause unpredictable behavior or incorrect floating point operations in the tracer process. The fix involves saving the floating point unit (FPU) register contents with save_fpu_regs() before invoking test_fp_ctl(), ensuring the tracer's register state is preserved correctly. This vulnerability is specific to the s390 architecture and the ptrace interface, affecting Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2023-52598 is primarily relevant to those using Linux systems on IBM Z mainframe hardware (s390 architecture), which is less common than x86_64 but still significant in sectors such as finance, government, and large enterprises that rely on mainframe computing for critical workloads. The vulnerability can lead to corruption of the tracer process's floating point control register, potentially causing incorrect computations, application crashes, or unstable behavior in debugging or tracing tools. This may affect the reliability and integrity of debugging sessions, potentially hindering incident response, forensic analysis, or development activities. While this vulnerability does not directly allow privilege escalation or remote code execution, the corruption of floating point registers could be exploited in complex attack chains or cause denial of service in critical debugging environments. The absence of known exploits reduces immediate risk, but organizations using s390 Linux systems should prioritize patching to maintain system stability and trustworthiness of debugging operations.

European organizations running Linux on s390 architecture should apply the official Linux kernel patch that addresses this vulnerability as soon as it becomes available from their distribution vendors or the Linux kernel mainline. Specifically, ensure that kernel versions include the fix that saves the FPU register contents before testing the fpc register value in ptrace operations. Additionally, organizations should audit and monitor the use of ptrace interfaces, especially in production environments, to limit exposure. Restrict ptrace usage to trusted users and processes through kernel.yama.ptrace_scope settings or similar security modules. Implement strict access controls and logging for debugging tools to detect anomalous ptrace activity. For critical systems, consider isolating debugging environments or using alternative debugging mechanisms that do not rely on ptrace. Regularly update and patch Linux kernels on s390 systems and maintain an inventory of affected systems to ensure timely remediation. Finally, educate developers and system administrators about the risks associated with ptrace misuse and floating point register corruption.