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Response snapshot Oct 30, 2026, 19:11 UTC

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VulnerabilityCVE-2026-90234

Linux kernel: NFS: Return a delegation the client fails to record

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.

At a glance

Exploited
Not known
Severity
7.5 High (CVSS 3.1)
Chance of exploitation
0.6% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-90234 (opens a new tab)

What happened

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.

Continue reading

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.

Scores and how they were measured

CVSS base severity

7.5

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.6%

Scored Percentile 50.2%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-90234 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  5. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-90234, scored 2026-10-30. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). Linux kernel: NFS: Return a delegation the client fails to record (CVE-2026-90234). https://kevwire.com/record/CVE-2026-90234

MLA

"Linux kernel: NFS: Return a delegation the client fails to record (CVE-2026-90234)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-90234.

Chicago

KEVWire. "Linux kernel: NFS: Return a delegation the client fails to record (CVE-2026-90234)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-90234.

Evidence summary (plain text)

Linux kernel: NFS: Return a delegation the client fails to record (Sep 17, 2026).
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.
CVSS 7.5 (version 3.1; evidence as of Oct 30, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-90234).
EPSS 0.6% for the following 30 days, scored Oct 30, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-90234&date=2026-10-30).
Sources:
NVD CVE-2026-90234: https://nvd.nist.gov/vuln/detail/CVE-2026-90234
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T13:06:45.042Z&lastModEndDate=2026-10-30T14:50:57.069Z&resultsPerPage=500&startIndex=1000
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T12:22:16.957Z&lastModEndDate=2026-10-30T14:05:57.373Z&resultsPerPage=500&startIndex=500
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T11:45:59.009Z&lastModEndDate=2026-10-30T13:20:57.281Z&resultsPerPage=500&startIndex=500
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-90234&date=2026-10-30
Record ID: CVE-2026-90234.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 30, 2026, 14:52 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

Record detail