CVE-2026-89701 nfsd: validate nseconds in TIME_DELEG decode paths
A missing validation in the Linux kernel NFS server allows remote attackers to cause a denial of service via malformed time values.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89701?
CVE-2026-89701 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: validate nseconds in TIME_DELEG decode paths
The xdrgen-based TIME_DELEG_ACCESS and TIME_DELEG_MODIFY decode arms store a raw uint32_t nseconds directly into tv_nsec without enforcing nseconds < NSEC_PER_SEC. The legacy nfsd4_decode_nfstime4 has this check but the TIME_DELEG paths do not. A malformed timespec can propagate through notify_change() to disk.
Add range checks in both nfs4xdr.c (SETATTR path) and nfs4callback.c (CB_GETATTR path).
Which versions are affected by CVE-2026-89701?
How do I fix CVE-2026-89701?
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-2026-89701 being exploited?
There is no known exploitation of CVE-2026-89701 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89701, DEBIAN-CVE-2026-89701, GHSA-pqvp-pfwp-hf4c, UBUNTU-CVE-2026-89701.