CVE-2026-89676 - Vulnerability Details

- nfsd: fix stale s2s_cp_stateids IDR entry for async COPY

Description

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

nfsd: fix stale s2s_cp_stateids IDR entry for async COPY

For an async COPY, nfsd4_copy() called nfs4_init_copy_state() before
dup_copy_fields(), so the s2s_cp_stateids IDR was pointed at
&u->copy->cp_stateid -- memory in the per-rqstp COMPOUND buffer that is
reused by the next request. dup_copy_fields() copies only the value into
async_copy, so the IDR slot dangled at the transient buffer for the whole
background copy. Any IDR walker then dereferences reused request memory:
the laundromat reads cs_type from it and, if the bytes look like an
expired NFS4_COPYNOTIFY_STID, follows into
refcount_dec()/idr_remove()/kfree() on garbage; manage_cpntf_state() has
the same exposure via idr_find().

Duplicate the fields first, then register the stateid on the stable
async_copy. result->cb_stateid is unchanged.

Published: 2026-09-11

Score: 9.8 Critical

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

The vulnerability arises when an asynchronous COPY operation in the NFSv4 server leaves a stale IDR entry pointing to a per‑request buffer that is subsequently reused. An IDR traversal that dereferences this dangling entry triggers kernel memory reclamation code to act on garbage, causing a kernel panic. This results in a denial of service. The weakness is classified as CWE-825, improper removal and deallocation of a resource. The CVSS score of 9.8 indicates a critical risk, and although the high.

Affected Systems

All Linux kernel builds that include the NFSv4 server with the async COPY feature enabled are vulnerable. The affected product is the Linux kernel. No precise version range is supplied by the CNA.

Risk and Exploitability

The likely attack vector involves an NFSv4 client issuing a manipulated asynchronous COPY request. Any remote NFS client can trigger the flaw, categorizing this vulnerability as critical. The EPSS score is below 1%, suggesting a very low exploitation probability, and the vulnerability is not listed in CISA’s KEV catalog. Consequently, the risk is moderate due to low exploitation likelihood, but if exploited it would cause a system crash.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`e0639dc5805a9d4faaa2c07ad98fa853b9529dd3`	affected	< 7aa34ea78f74e6ef60c8112635a87fc43d57f6c9
`e0639dc5805a9d4faaa2c07ad98fa853b9529dd3`	affected	< 9b4e5e9ba5ae13808b8a6d229d87c54611ba0e7a
`e0639dc5805a9d4faaa2c07ad98fa853b9529dd3`	affected	< 14b978e8d05ce018d0afbeb6611833ef91713a02
`e0639dc5805a9d4faaa2c07ad98fa853b9529dd3`	affected	< d0beaee498e11880e72826026db0e9c9890fc114

Linux

affected

Version	Status	Constraints
`4.20`	affected	—
`0`	unaffected	< 4.20
`6.12.111`	unaffected	≤ 6.12.*
`6.18.50`	unaffected	≤ 6.18.*
`7.2.4`	unaffected	≤ 7.2.*
`7.3-rc1`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[e0639dc5805a9d4faaa2c07ad98fa853b9529dd3,9b4e5e9ba5ae13808b8a6d229d87c54611ba0e7a]`	affected	code_commit	—
`[e0639dc5805a9d4faaa2c07ad98fa853b9529dd3,14b978e8d05ce018d0afbeb6611833ef91713a02]`	affected	code_commit	—
`[e0639dc5805a9d4faaa2c07ad98fa853b9529dd3,d0beaee498e11880e72826026db0e9c9890fc114]`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`4.20`	affected	generic	—
`[0,4.20)`	unaffected	semver	—
`[6.18.50,6.18.*]`	unaffected	generic	—
`[7.2.4,7.2.*]`	unaffected	generic	—
`[7.3-rc1,*]`	unaffected	generic	—

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Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Apply the kernel update that contains the NFSv4 async COPY patch to remove the stale IDR issue.
If the update is not available, disable the async COPY feature in operations to be synchronous to avoid the stale IDR condition.
Enable kernel IDR debugging and configure the system logger to alert on IDR misuse, then monitor logs for anomalous errors related to NFSv4 COPY operations.

Generated by OpenCVE AI on September 15, 2026 at 20:22 UTC.

Tracking

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Advisories

Source	ID	Title
Debian DSA	DSA-6528-1	linux security update

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00671.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/14b978e8d05ce018d0afbeb6611833ef91713a02
https://git.kernel.org/stable/c/7aa34ea78f74e6ef60c8112635a87fc43d57f6c9
https://git.kernel.org/stable/c/9b4e5e9ba5ae13808b8a6d229d87c54611ba0e7a
https://git.kernel.org/stable/c/d0beaee498e11880e72826026db0e9c9890fc114
https://nvd.nist.gov/vuln/detail/CVE-2026-89676
https://www.cve.org/CVERecord?id=CVE-2026-89676

History

Mon, 21 Sep 2026 13:30:00 +0000

Type	Values Removed	Values Added
References		https://git.kernel.org/stable/c/7aa34ea78f74e6ef60c8112635a87fc43d57f6c9

Sun, 13 Sep 2026 06:45:00 +0000

Type	Values Removed	Values Added
Metrics	cvssV3_1 `{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}`	cvssV3_1 `{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}`

Sat, 12 Sep 2026 00:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-825
References		https://nvd.nist.gov/vuln/detail/CVE-2026-89676 https://www.cve.org/CVERecord?id=CVE-2026-89676
Metrics	threat_severity `None`	cvssV3_1 `{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}` threat_severity `Moderate`

Fri, 11 Sep 2026 23:45:00 +0000

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: nfsd: fix stale s2s_cp_stateids IDR entry for async COPY For an async COPY, nfsd4_copy() called nfs4_init_copy_state() before dup_copy_fields(), so the s2s_cp_stateids IDR was pointed at &u->copy->cp_stateid -- memory in the per-rqstp COMPOUND buffer that is reused by the next request. dup_copy_fields() copies only the value into async_copy, so the IDR slot dangled at the transient buffer for the whole background copy. Any IDR walker then dereferences reused request memory: the laundromat reads cs_type from it and, if the bytes look like an expired NFS4_COPYNOTIFY_STID, follows into refcount_dec()/idr_remove()/kfree() on garbage; manage_cpntf_state() has the same exposure via idr_find(). Duplicate the fields first, then register the stateid on the stable async_copy. result->cb_stateid is unchanged.
Title		nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/14b978e8d05ce018d0afbeb6611833ef91713a02 https://git.kernel.org/stable/c/9b4e5e9ba5ae13808b8a6d229d87c54611ba0e7a https://git.kernel.org/stable/c/d0beaee498e11880e72826026db0e9c9890fc114

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-09-11T19:46:00.382Z

Updated: 2026-09-21T13:14:43.984Z

Reserved: 2026-09-11T19:38:34.747Z

Link: CVE-2026-89676

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-09-11T20:19:54.273

Modified: 2026-09-21T14:17:25.073

Link: CVE-2026-89676

Redhat

Severity : Moderate

Publid Date: 2026-09-11T19:46:00Z

Links: CVE-2026-89676 - Bugzilla

OpenCVE Enrichment

Updated: 2026-09-15T20:30:10Z

Weaknesses

CWE-825
Expired Pointer Dereference

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

Subscriptions

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