kernel: nfsd: hold rcu across localio cmpxchg retry (CVE-2026-89670)

Overview

A flaw was found in the Linux kernel's Network File System Daemon (nfsd) component. A race condition exists in the nfsd_open_local_fh() function where an nfsd_file object can be freed and its memory recycled while another process attempts to access it. This can lead to a use-after-free vulnerability, allowing an attacker to potentially cause memory corruption, disclose sensitive information, or execute arbitrary code.

Vendor advisories

• Red Hat VEX · Moderate · affected: Red Hat Enterprise Linux 10 · no fix planned: Red Hat Enterprise Linux 10 · updated 2026-10-21 · vex

kernel: nfsd: hold rcu across localio cmpxchg retry — rated Moderate by Red Hat. Released 2026-09-11, updated 2026-10-21.

Affected:

• Red Hat Enterprise Linux 10

No fix planned:

• Red Hat Enterprise Linux 10

Not affected:

• Red Hat Enterprise Linux 6
• Red Hat Enterprise Linux 7
• Red Hat Enterprise Linux 8
• Red Hat Enterprise Linux 9
• Red Hat OpenShift Container Platform 4

Remediation

Fix deferred

Workarounds / mitigations:

• Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.