CVE-2026-89689
A critical flaw in the Linux kernel’s NFS server (nfsd) implementation allows the kernel to free session slots that are still in use, causing memory corruption. The bug occurs when the session shrinker reduces the maximum slot count while a client continues to reference slots in the higher range, and the code fails to verify that the current slot is within the new limit and that the slot is not actively in use before freeing it.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Any system running a vulnerable Linux kernel version that includes the flawed nfsd code.
Real-world impact
An attacker controlling a NFS client could trigger the flaw to corrupt kernel memory, potentially leading to arbitrary code execution or system compromise.
Why this severity
The CVSS score of 9.8 reflects critical severity due to remote exploitability, no authentication required, and the potential for full system compromise through memory corruption.
What to do about it
- 011. Update the Linux kernel to a version that includes the fix for CVE-2026-89689.
- 022. Reboot the system (or restart the NFS service) to load the patched kernel.
NVD-referenced Linux kernel advisory
Timeline
- Sep 11, 2026 · 2d agoPublishedDisclosed and added to the National Vulnerability Database.
- Sep 13, 2026 · 7h agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.