CVE-2026-89699 nfsd: validate symlink target length in NFSv4 CREATE
A remote attacker can cause memory exhaustion in the Linux kernel NFS server by sending oversized symlink targets, leading to 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-2026-89699?
CVE-2026-89699 is a high-severity 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: validate symlink target length in NFSv4 CREATE
nfsd4_decode_create() accepts an unbounded cr_datalen from the wire for NF4LNK symlink targets, allowing a client to force a kmalloc of up to the maximum RPC payload size (several MiB) per COMPOUND op that persists until compound teardown. The VFS rejects oversized targets with ENAMETOOLONG, but the allocation has already occurred.
Reject cr_datalen == 0 early with nfserr_inval and cr_datalen greater than NFS4_MAXPATHLEN (PATH_MAX) with nfserr_nametoolong to bound the allocation.
Which versions are affected by CVE-2026-89699?
How do I fix CVE-2026-89699?
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-2026-89699 being exploited?
There is no known exploitation of CVE-2026-89699 in the wild and no public exploit code.
Sources
Also known as AZL-100310, BELL-CVE-2026-89699, DEBIAN-CVE-2026-89699, GHSA-864v-pq9r-vg9w, UBUNTU-CVE-2026-89699.