CVE-2024-57951: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-57951 is a vulnerability in the Linux kernel's hrtimers subsystem, discovered and disclosed in February 2025. The issue affects multiple versions of the Linux kernel, including versions from 4.19.302 up to 4.20, 5.4.264 up to 5.4.290, 5.10.204 up to 5.10.234, and 5.15.143 up to 5.15.177 (NVD).

The vulnerability occurs during CPU hotplug operations when a CPU transitions from CPUHP_ONLINE to CPUHP_HRTIMERS_PREPARE and back to CPUHP_ONLINE. During this transition, cpu_base.hres_active remains incorrectly set to 1, while the tick and clockevents are shut down at CPUHP_AP_TICK_DYING. This leads to incorrect assumptions about the hrtick's active state and prevents the clockevent device from transitioning to oneshot mode. Additionally, cpu_base.online is not properly set after the transition, causing WARN_ON_ONCE in enqueue_hrtimer() and potentially leaving dangling pointers (Kernel Patch). The vulnerability has been assigned a CVSS v3.1 base score of 7.8 (High) with vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD).

The vulnerability can lead to system instability and potential security risks due to incorrect CPU state handling during hotplug operations. The issue can result in dangling pointers in the worst case, which could lead to memory corruption or system crashes (Kernel Patch).

The issue has been fixed by adding a corresponding startup() callback that resets the stale per CPU state and sets the online flag correctly. The fix includes making the new callback unconditionally available and modifying the state clearing process in the starting callback (Kernel Patch). Ubuntu and other distributions have begun releasing patches for affected versions (Ubuntu Security).