CVE-2026-23053

Vulnerability

A deadlock in the Linux kernel's NFS subsystem (NFSv4.1) was discovered, involving a circular dependency between memory reclaim and NFS state recovery. When kthreadd attempts to reclaim memory via nfs_release_folio(), it may block if NFS state recovery is underway, but state recovery itself cannot proceed because it is waiting for kthreadd. This creates a deadlock.

Exploitation

An attacker with local access can trigger memory pressure while NFS state recovery is needed, for example by exhausting memory or initiating a forced unmount. The deadlock does not require authentication to the NFS server, but the system must be an NFS client with NFSv4.1 mount. No special network position is required beyond normal NFS client operation.

Impact

The deadlock results in a complete system hang, as both kthreadd and NFS recovery threads become stuck. This leads to denial of service, rendering the system unresponsive. No privilege escalation or data corruption is reported.

Mitigation

The fix involves modifying nfs_release_folio() to kick off writeback or an asynchronous commit without waiting for completion, breaking the circular dependency. Patches were applied to the stable kernel trees as commits [1] and [2]. Users should update to kernels containing these fixes.