CVE-2023-53093 is a vulnerability in the Linux kernel's tracing subsystem, specifically related to the handling of histogram values in kernel tracing events. The vulnerability arises because the histogram code was not designed to handle certain modifiers such as strings, stacktraces, graphs, symbols, syscalls, or grouping in buckets or logarithmic scales. When such unsupported modifiers are applied to histogram values, the kernel tracing subsystem fails to validate these inputs properly, leading to a NULL pointer dereference and a kernel oops (crash). This is demonstrated by the example where a crafted kprobe event with histogram modifiers causes the kernel to abort due to a level 0 translation fault, resulting in a segmentation fault and system instability. The root cause is that the histogram code does not check for invalid modifiers before processing, causing it to dereference a NULL pointer. This vulnerability affects Linux kernel versions including the one identified by the commit hash c6afad49d127f6d7c9957319f55173a2198b1ba8. Although no known exploits are reported in the wild, the vulnerability allows a local user with permissions to write to tracing events (typically root or privileged users) to cause a denial of service by crashing the kernel. The issue was reported by Mark Rutland and has been addressed by adding validation to reject unsupported modifiers for histogram values in tracing events, preventing the kernel crash.

The primary impact of CVE-2023-53093 is a denial-of-service (DoS) condition caused by a kernel crash triggered through the Linux kernel tracing subsystem. For European organizations, this vulnerability could disrupt critical systems running Linux kernels with the affected tracing code, especially in environments relying on kernel tracing for performance monitoring or debugging. Systems that allow untrusted or less-trusted users to configure tracing events are at higher risk, as exploitation requires local access with permissions to modify tracing events. The crash could lead to system downtime, loss of availability, and potential disruption of services, which is critical for infrastructure providers, cloud services, and enterprises relying on Linux-based servers. While this vulnerability does not directly lead to privilege escalation or data leakage, the resulting instability could be leveraged as part of a broader attack chain or cause operational disruptions. Given the widespread use of Linux in European data centers, cloud environments, and embedded systems, the impact could be significant if exploited in sensitive or high-availability environments.

1. Apply the official Linux kernel patches that address this vulnerability as soon as they become available from trusted sources or Linux distribution vendors. 2. Restrict access to the tracing subsystem by limiting permissions to only trusted administrators and users; ensure that only authorized personnel can write to /sys/kernel/tracing/kprobe_events and related tracing interfaces. 3. Monitor kernel logs and tracing subsystem activity for unusual or unauthorized modifications to tracing events that could indicate exploitation attempts. 4. Disable or restrict kernel tracing features on production systems where tracing is not required, reducing the attack surface. 5. Implement strict access controls and auditing on systems that allow local user access, especially in multi-tenant or shared environments. 6. For embedded or specialized Linux systems, verify kernel versions and apply backported patches if necessary to mitigate the vulnerability. 7. Incorporate this vulnerability into vulnerability management and incident response plans to ensure rapid detection and remediation.