CVE-2026-89711 Linux kernel NFSD - Broken Authentication

Linux kernel NFSD contains a broken authentication vulnerability caused by flawed WARN_ON_ONCE usage in nfsd_mode_check, letting attackers cause improper error handling during NFS reexport, exploit requires NFS filesystem export with specific dentry conditions.

CVSS base score 8.2 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.44% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Broken Authentication
Impact
Denial Of Service
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Published
11 September 2026
Updated
15 October 2026

Vendor fix

Update to the latest Linux kernel version containing the fix that removes WARN_ON_ONCE from nfsd_mode_check.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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