The vulnerability in the Linux kernel IPv6 subsystem arises from a race condition in the rt6_get_pcpu_route() function on PREEMPT_RT kernels. When rt6_get_pcpu_route() returns NULL, the current task may be preempted, allowing another task on the same CPU to install a per-CPU route entry. Upon resumption, the first task's cmpxchg() operation fails because the route entry is no longer NULL, triggering a BUG_ON() and causing a kernel bug. The fix involves gracefully handling the cmpxchg() failure by freeing the allocation and returning the existing route entry, and replacing BUG_ON with WARN_ON_ONCE for non-PREEMPT_RT kernels where such races are unexpected. This vulnerability can cause kernel crashes (denial of service). The issue is patched in updated Linux kernel versions as indicated by the extensive list of affected versions and corresponding fixed releases. The vendor advisory from Ubuntu confirms the availability of patches and recommends updating to fixed kernel versions.

This vulnerability can cause a kernel BUG_ON() to be triggered, leading to a kernel crash and denial of service on affected systems running PREEMPT_RT kernels. There is no indication of confidentiality or integrity impact. The CVSS score of 7.5 reflects a medium severity due to the potential for system instability or downtime. No known exploits in the wild have been reported.

A patch is available and should be applied by updating the Linux kernel to the fixed versions provided by the vendor. For Ubuntu systems, the advisory USN-8162-1 and USN-8177-1 provide fixed package versions, including linux-image-5.15.0-1057-nvidia-tegra and linux-image-6.17.0-1010-realtime among others. After updating, a system reboot is required to apply the fix. Due to ABI changes, recompilation and reinstallation of third-party kernel modules may be necessary. No other mitigations are indicated or required.