CVE-2026-89679

Status: UPDATED  |  Advisory ID: CVE-2026-89679

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

nfsd: fix null dereference in nfsd4_setattr for deleg timestamp attrs

When a SETATTR request includes FATTR4_WORD2_TIME_DELEG_ACCESS or

FATTR4_WORD2_TIME_DELEG_MODIFY in the attribute bitmap, nfsd4_setattr()

sets deleg_attrs=true and calls nfs4_preprocess_stateid_op() to validate

the stateid.

If the client supplies the NFSv4 "one stateid" (all-0xFF bytes),

check_special_stateids() returns nfs_ok without populating the output

nfs4_stid pointer, because the special-stateid path in

nfs4_preprocess_stateid_op() jumps to done: with s==NULL, and the

"if (s)" block that would set *cstid is skipped. The local variable `st`

remains NULL.

Back in nfsd4_setattr(), the if (deleg_attrs) block then unconditionally

dereferences st->sc_type (at offset 4 from NULL), causing a kernel oops.

This is remotely triggerable by any NFSv4 client: send COMPOUND [PUTROOTFH,

SETATTR(ONE_STATEID, {bmval2=FATTR4_WORD2_TIME_DELEG_ACCESS, ...})].

No authentication, delegation, or prior state is required.

Fix by adding a NULL check before the dereference. A special stateid is

not a delegation stateid, so the existing nfserr_bad_stateid return value

is already correct; we only need to guard the pointer dereference itself. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References