CVE-2025-21900 NFSv4: Fix a deadlock when recovering state on a sillyrenamed file
A race condition in the Linux kernel NFSv4 implementation can cause a deadlock during state recovery, leading to 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-2025-21900?
CVE-2025-21900 is a high-severity vulnerability in Linux kernel, published on 1 Apr 2025. 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:
NFSv4: Fix a deadlock when recovering state on a sillyrenamed file
If the file is sillyrenamed, and slated for delete on close, it is possible for a server reboot to triggeer an open reclaim, with can again race with the application call to close(). When that happens, the call to put_nfs_open_context() can trigger a synchronous delegreturn call which deadlocks because it is not marked as privileged.
Instead, ensure that the call to nfs4_inode_return_delegation_on_close() catches the delegreturn, and schedules it asynchronously.
Weakness: CWE-667
Which versions are affected by CVE-2025-21900?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21900?
Apply the vendor's patch.
Is CVE-2025-21900 being exploited?
There is no known exploitation of CVE-2025-21900 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21900, DEBIAN-CVE-2025-21900, GHSA-5px9-qgxf-p79c, UBUNTU-CVE-2025-21900.