CVE-2026-89685 Linux CVE debrief

Who should care

Linux system administrators and security teams, especially those using nfsd, should assess exposure and verify the presence of the fix in their systems to prevent potential denial of service for all non-reclaim operations and increased risk of resource exhaustion.

Why it matters

A vulnerability in the Linux kernel's nfsd subsystem can cause a clock domain mismatch, potentially allowing an attacker to block all non-reclaim operations for all other clients. Linux system administrators and security teams should prioritize verifying the presence of the fix in their systems.

• Potential denial of service for all non-reclaim operations
• Increased risk of resource exhaustion
• Need for verification of fix presence in Linux kernel

Technical summary

The clients_still_reclaiming() function in the Linux kernel's nfsd subsystem incorrectly compares a deadline computed from nn->boot_time (CLOCK_REALTIME) against ktime_get_boottime_seconds() (CLOCK_BOOTTIME). This comparison always fails, allowing a client to hold the server in grace indefinitely by sending CLAIM_PREVIOUS OPEN requests. The issue has been resolved by adding boot_time_bt (CLOCK_BOOTTIME) alongside the existing boot_time and using it for the deadline computation. Linux system administrators and security teams should prioritize verifying the presence of the fix in their systems, especially those using nfsd, to prevent potential denial of service for all non-reclaim operations and increased risk of

Defensive priority

Linux system administrators and security teams should prioritize verifying the presence of the fix in their systems, especially those using nfsd.

Recommended defensive actions

• Verify the presence of the fix in the Linux kernel
• Update to the latest Linux kernel version if necessary
• Monitor nfsd subsystem for potential issues
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details about the vulnerability and its resolution. However, the corpus does not establish versions, exploitation, impact, or remediation beyond the provided information, requiring verification from the supplied official sources.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.