CVE-2026-43420 addresses a vulnerability in the Linux kernel's Ceph filesystem related to the asynchronous unlink operation. The issue arises because the i_nlink counter is decremented prematurely before the unlink completion is confirmed, which can race with other operations and cause an underrun of the i_nlink counter. This underrun triggers kernel warnings and indicates improper inode link count management during async unlink. The fix involves adding proper locking to prevent decrementing i_nlink when it is already zero, avoiding race conditions.