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PatchSiren cyber security CVE debrief

CVE-2026-89711 Linux CVE debrief

A flaw was found in the Linux kernel's NFSD implementation. The WARN_ON_ONCE in nfsd_mode_check was flawed and has been removed. This change was made to prevent potential kernel warnings that could occur when NFSD exports an NFS filesystem. The removal of this WARN_ON_ONCE is crucial for maintaining system stability and preventing unnecessary warnings. Linux kernel developers and administrators should review the patch and apply it to ensure the flaw is addressed. The patch prevents potential kernel warnings related to NFSD exports of NFS filesystems, which could impact system performance and security.

Vendor
Linux
Product
Unknown
CVSS
HIGH 8.2
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-11
Original CVE updated
2026-10-19
Advisory published
2026-09-11
Advisory updated
2026-10-19

Who should care

Linux kernel developers and administrators responsible for maintaining and securing Linux systems using NFSD. These individuals should review the patch and apply it to ensure the flaw is addressed. They should also verify Linux kernel versions and apply updates as necessary to prevent potential kernel warnings related to NFSD exports of NFS filesystems.

Why it matters

A flaw in the Linux kernel's NFSD implementation was found and addressed. Defenders should verify Linux kernel versions, apply patches, and monitor for potential kernel warnings.

  • Verification of Linux kernel versions and patch application is necessary to prevent potential kernel warnings.
  • Monitoring for kernel warnings related to NFSD exports of NFS filesystems is recommended.
  • Defenders should review and apply the patch to ensure the flaw is addressed.

Technical summary

The Linux kernel's NFSD implementation had a flawed WARN_ON_ONCE in nfsd_mode_check. This has been removed to prevent potential kernel warnings when NFSD exports an NFS filesystem. The removal of this WARN_ON_ONCE is crucial for maintaining system stability and preventing unnecessary warnings. The flaw was identified in the Linux kernel's NFSD implementation, and the removal of the WARN_ON_ONCE is intended to prevent potential kernel warnings. Defenders should review and apply the patch to ensure the flaw is addressed.

Defensive priority

Medium

Recommended defensive actions

  • Review and apply the patch to remove the flawed WARN_ON_ONCE from nfsd_mode_check
  • Monitor for potential kernel warnings related to NFSD exports of NFS filesystems
  • Verify the Linux kernel version and apply updates as necessary
  • Perform a thorough review of the system to identify potential exposure
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented.
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and source item provide details about the flaw in the Linux kernel's NFSD implementation. The WARN_ON_ONCE in nfsd_mode_check was removed due to its flawed assumption. The source item and CVE record are the primary sources of information. The flaw was identified in the Linux kernel's NFSD implementation, and the removal of the WARN_ON_ONCE is intended to prevent potential kernel warnings. Defenders should verify Linux kernel versions and apply patches to ensure the flaw is addressed. The source item provides additional

Sources and references

Verified primary and authoritative sources

  • CVE-2026-89711 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-89711

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-89711 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-89711

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/89xxx/CVE-2026-89711.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/ae251937c6f0237e5b555a5e4ba4595b8206e865

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/e145e8d67a5d41c72d322e7f87ab474d39d9dfb7

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9f4434893a2783f7384d993cea883aff3fb7a52d

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/2ef131323999539038e306773c8256403834361b

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/b55b4d880bb080fa10eb08ba21a5d8679b8102fe

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/7ef182a8fe9c12b0d936880b1e504840639aa009

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/a275de3bac5635514ca830f2e46b5ff0e66b5c4c

    Supplemental source

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.