CVE-2026-89683 nfsd: fix dentry ref leak on V4ROOT export filehandle lookup
A crafted NFSv3 filehandle targeting a V4ROOT export causes a dentry reference leak, 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-2026-89683?
CVE-2026-89683 is a denial of service 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 dentry ref leak on V4ROOT export filehandle lookup
nfsd_set_fh_dentry() leaks the dentry reference from exportfs_decode_fh_raw() when the NFS3_FHSIZE or NFS_FHSIZE switch cases detect NFSEXP_V4ROOT and goto out. The out: label calls exp_put() but never dput(dentry), and fhp->fh_dentry was never assigned so fh_put() cannot compensate.
A crafted NFSv3 filehandle targeting a V4ROOT export's fsid triggers the leak on every request.
Which versions are affected by CVE-2026-89683?
How do I fix CVE-2026-89683?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-89683 being exploited?
There is no known exploitation of CVE-2026-89683 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89683, DEBIAN-CVE-2026-89683, GHSA-58hv-jwv2-hff3, UBUNTU-CVE-2026-89683.