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CVE Record

CVE-2026-22989: nfsd: check that server is running in unlock_filesystem

In the Linux kernel, the following vulnerability has been resolved: nfsd: check that server is running in unlock_filesystem If we are trying to unlock the filesystem via an administrative interface and nfsd isn't running, it crashes the server. This happens currently because nfsd4_revoke_states() access state structures (eg., conf_id_hashtbl) that has been freed as a part of the server shutdown. [ 59.465072] Call trace: [ 59.465308] nfsd4_revoke_states+0x1b4/0x898 [nfsd] (P) [ 59.465830] write_unlock_fs+0x258/0x440 [nfsd] [ 59.466278] nfsctl_transaction_write+0xb0/0x120 [nfsd] [ 59.466780] vfs_write+0x1f0/0x938 [ 59.467088] ksys_write+0xfc/0x1f8 [ 59.467395] __arm64_sys_write+0x74/0xb8 [ 59.467746] invoke_syscall.constprop.0+0xdc/0x1e8 [ 59.468177] do_el0_svc+0x154/0x1d8 [ 59.468489] el0_svc+0x40/0xe0 [ 59.468767] el0t_64_sync_handler+0xa0/0xe8 [ 59.469138] el0t_64_sync+0x1ac/0x1b0 Ensure this can't happen by taking the nfsd_mutex and checking that the server is still up, and then holding the mutex across the call to nfsd4_revoke_states().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel NFS server bug can crash a host when an administrative filesystem unlock operation occurs after nfsd has stopped. The described impact is availability loss, not data theft or remote code execution. No provided source reports active exploitation.

Executive priority

Treat as a targeted availability risk for NFS-serving Linux hosts. Prioritize patch validation in infrastructure where an unexpected kernel crash would disrupt storage, virtualization, backup, or shared filesystem workflows.

Technical view

nfsd unlock_filesystem could call nfsd4_revoke_states() after nfsd shutdown freed state structures such as conf_id_hashtbl. The resolved change takes nfsd_mutex, verifies the server is still running, and holds the mutex while revoking states.

Likely exposure

Exposure is most likely on Linux systems running affected kernel versions with the NFS server component in use. The source names Linux kernel versions around 6.9 through later affected ranges, but exact distribution package mapping is not provided.

Exploitation context

The source describes triggering through an administrative interface when nfsd is not running. It does not establish remote exploitation, privilege requirements beyond administrative interface access, public exploit availability, or active exploitation. KEV status is false in the supplied bundle.

Researcher notes

Evidence supports a race/lifecycle bug in nfsd shutdown state handling. The bundle lacks CVSS, CWE, distribution package data, and exploit confirmation. Avoid assuming network reachability alone is sufficient without administrative interface access evidence.

Mitigation direction

  • Check vendor kernel advisories for your distribution's fixed package versions.
  • Prioritize updates on Linux hosts that provide NFS services.
  • Avoid unnecessary administrative unlock operations on stopped nfsd services until patched.
  • Track the referenced stable kernel fixes in affected kernel maintenance branches.

Validation and detection

  • Inventory Linux hosts with NFS server functionality enabled or recently used.
  • Map running kernels to vendor advisories or upstream fixed stable commits.
  • Review crash logs for nfsd4_revoke_states or write_unlock_fs call traces.
  • Confirm patched systems include the nfsd_mutex server-running check behavior.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2026-22989 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1ac3629bf012592cb0320e52a1cceb319a05ad17, 1ac3629bf012592cb0320e52a1cceb319a05ad17, 1ac3629bf012592cb0320e52a1cceb319a05ad17unaffected
LinuxLinux6.9, 0, 6.12.66, 6.18.6, 6.19affected
Weakness

CWE details

No CWE listed

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