CVE-2026-90234

/// Technical description

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 offer

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References