Linux Kernel NFS client Vulnerability Rated 7.5 CVSS

Status: UPDATED  |  Advisory ID: CVE-2026-90234

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

NFS: Return a delegation the client fails to record

When an NFS server grants a delegation in an OPEN reply,

nfs_inode_set_delegation() records it on the client. However, three

of its error flows return without sending DELEGRETURN.

A delegation can be relinquished only by DELEGRETURN (RFC 8881

Section 20.2.4), so dropping one silently leaves the server believing

the client still holds it. If the server happens to recall that

delegation, the client answers CB_RECALL with NFS4ERR_BADHANDLE

because it has no record of the stateid. The server revokes the

delegation and moves it onto its cl_revoked list, because the client

never sends the FREE_STATEID that would drain it. Every subsequent

SEQUENCE reply then carries SEQ4_STATUS_RECALLABLE_STATE_REVOKED,

and the client's state manager loops issuing TEST_STATEID across its

delegations without ever clearing the condition.

The window is easy to reach now that a server offers a write

delegation on any write OPEN: a delegation recalled for one opener

races a re-open that the server answers with a fresh write

delegation.

Instead of dropping it, hand the delegation back during these error

flows. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References