In the Linux kernel, the following vulnerability has been resolved: kprobes: Fix permanent hang when flushing the kprobe optimizer Writing 0 to… (CVE-2026-98530)

The Linux kernel kprobes subsystem had a flaw where writing 0 to /proc/sys/debug/kprobes-optimization while a kprobe was jump-optimized caused the writing process to hang indefinitely. This occurs because the writer sleeps in an uninterruptible state (D state) holding the kprobe_sysctl_mutex, blocking any further access to the sysctl. The root cause is that the completion mechanism used to signal the optimizer flush never completes while a waiter is sleeping, due to reinitialization and improper synchronization between multiple flushers. The fix replaces the completion with a counter of optimizer passes that is incremented and signaled under mutex protection, allowing multiple flushers to wait concurrently without deadlock.

The vulnerability causes a permanent hang (deadlock) in processes attempting to write to or read from the kprobes optimization sysctl interface. This can lead to system instability or unresponsiveness for affected processes. There is no indication of privilege escalation or code execution impact. The issue affects system reliability when interacting with kprobes optimization controls.

A fix has been implemented in the Linux kernel to replace the completion mechanism with a counter and proper synchronization to prevent the hang. Users should apply the official kernel update that includes this fix. Since this is a kernel-level issue, upgrading to a patched kernel version is the recommended remediation. No alternative workarounds are indicated.