CVE-2026-89679
Received
Received - Intake
Null pointer dereference in Linux kernel NFS server
Vulnerability report for CVE-2026-89679, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-11
Last updated on: 2026-09-11
Assigner: kernel.org
Description
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | * |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
