CVE-2026-89676

/// Technical description

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

nfsd: fix stale s2s_cp_stateids IDR entry for async COPY

For an async COPY, nfsd4_copy() called nfs4_init_copy_state() before

dup_copy_fields(), so the s2s_cp_stateids IDR was pointed at

&u->copy->cp_stateid -- memory in the per-rqstp COMPOUND buffer that is

reused by the next request. dup_copy_fields() copies only the value into

async_copy, so the IDR slot dangled at the transient buffer for the whole

background copy. Any IDR walker then dereferences reused request memory:

the laundromat reads cs_type from it and, if the bytes look like an

expired NFS4_COPYNOTIFY_STID, follows into

refcount_dec()/idr_remove()/kfree() on garbage; manage_cpntf_state() has

the same exposure via idr_find().

Duplicate the fields first, then register the stateid on the stable

async_copy. result->cb_stateid is unchanged.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References