CVE-2026-89681 nfsd: fix layout fence worker double-reference race
A race condition in the Linux kernel NFS server allows a double-reference leak, potentially leading to resource exhaustion and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89681?
CVE-2026-89681 is a critical vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix layout fence worker double-reference race
The workqueue core clears WORK_STRUCT_PENDING before the callback is invoked, so delayed_work_pending() in lm_breaker_timedout() can return false while the fence worker is already running. This lets the breaker take a duplicate sc_count reference and schedule a new worker that coalesces with the in-progress one. The extra reference is never put, leaking the layout stateid.
Replace the racy delayed_work_pending() check with an ls_fence_inflight boolean set atomically with refcount_inc_not_zero() under ls_lock, and cleared under ls_lock before the final nfs4_put_stid() on the dispose path; the retry path intentionally retains it. Remove the self-rearm mod_delayed_work() at the top of the worker.
Which versions are affected by CVE-2026-89681?
How do I fix CVE-2026-89681?
Apply the vendor's patch.
Is CVE-2026-89681 being exploited?
There is no known exploitation of CVE-2026-89681 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-89681, GHSA-3x6w-r97p-5874, UBUNTU-CVE-2026-89681.