A Linux kernel nfsd vulnerability impacts widely used kernels/distributions and NFS servers; can crash or enable kernel compromise across enterprises.
CVE-2026-89659
Use-after-free in Linux NFS server (nfsd) delegation revoke.
Is CVE-2026-89659 being exploited?
Not confirmed. CVE-2026-89659 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.43% probability of exploitation in the next 30 days.
How severe is CVE-2026-89659?
CVE-2026-89659 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-89659?
Yes. A fix has been recorded for CVE-2026-89659. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-89659 affect?
CVE-2026-89659 affects Linux kernel (nfsd) - NFS server, Enterprise Linux distributions (kernel packages), NAS appliances using Linux kernel. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-89659?
Apply vendor/kernel updates that include the fix and restart NFS services; block untrusted NFS clients if immediate patching impossible.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote NFS client can trigger a kernel use-after-free causing memory corruption, crash (DoS) or possible privilege escalation/remote code execution.
Immediate action required
- affected>= 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 and < 3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3
- affected>= 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 and < 2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56
- affected>= 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 and < 4683ca76b3b7e5808338491c6eb3c20e6b4894d5
- affected3.10
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.