CVE-2026-89687 nfsd: ensure nfsd_file_do_acquire() does not use a non-opened file
A flaw in the Linux kernel NFS server could lead to a null pointer dereference if a file is not properly opened, causing a 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-2026-89687?
CVE-2026-89687 is a high-severity 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: ensure nfsd_file_do_acquire() does not use a non-opened file
->atomic_open is permitted to return success without actually opening the file. It indicates this by calling finish_no_open(). This means dentry_create() can return a file which hasn't been opened. This is extremely unlikely as ->atomic_open handlers typically use finish_no_open() only for already existing files, and dentry_create() isn't called in that case, and the parent being locked should prevent races.
However out of an abundance of caution it seems wise to teach nfsd to only use the file returned by dentry_create() if FMODE_OPENED is set, indicating that it has in fact been opened.
Which versions are affected by CVE-2026-89687?
How do I fix CVE-2026-89687?
Apply the vendor's patch.
Is CVE-2026-89687 being exploited?
There is no known exploitation of CVE-2026-89687 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-89687, GHSA-vpqx-gvmc-m7vf, UBUNTU-CVE-2026-89687.