In the Linux kernel, the following vulnerability has been resolved:

nfsd: check client ownership when cancelling a copy-notify stateid

On the OFFLOAD_CANCEL path (clp != NULL), manage_cpntf_state() freed the
target cpntf state without checking ownership. The lookup key
st->si_opaque.so_id is allocated cyclically (guessable) and the embedded
clientid is the fixed per-net nn->s2s_cp_cl_id, so any authenticated
NFSv4.2 client could cancel and free another client's copy-notify
stateid.

Compare the creating clientid recorded in state->cp_p_clid against the
requesting client's cl_clientid and return nfserr_bad_stateid on a
mismatch instead of freeing the entry.