cve 2025 68209

CVE-2025-68209 is a Linux kernel vulnerability in the Mellanox/NVIDIA mlx5 driver that was fixed in mid-December. The issue involves unsafe default values used when creating Completion Queues (CQs), which could lead to a kernel null-pointer fault. Specifically, a polling-only kernel CQ could be spuriously triggered and dereference a user-only completion callback, causing a kernel crash. The fix is a small, surgical patch that corrects the default initialization to prevent this stability hole. This tag covers discussions about the vulnerability, its impact on kernel stability, and the patch that resolves it.