A vulnerability in the Linux kernel's SELinux and SMACK security modules allowed the root user on an NFS client to bypass permission checks and change security labels on files in an NFS filesystem exported with root squashing enabled. This was due to improper permission checks in the inode_setsecctx hook. The issue has been resolved by replacing a call to __vfs_setxattr_noperm() with __vfs_setxattr_locked(), ensuring proper permission enforcement and handling of conflicting delegations.