High 8.2Published Sep 11, 2026

CVE-2026-89711NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check

Updated under an hour ago (Oct 27, 2026, 8:30 PM ET)

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check The header for commit e75b23f9e323 ("nfsd: check d_can_lookup in fh_verify of directories") details the assumption that justified adding the WARN_ON_ONCE to nfsd_mode_check(), that assumption is invalid (in the case of NFS reexport). When NFSD exports an NFS filesystem it is very possible for nfsd_mode_check() to encounter a @dentry that doesn't have i_op->lookup (see nfs_fhget()'s NFS_ATTR_FATTR_MOUNTPOINT and NFS_ATTR_FATTR_V4_REFERRAL handling, and d_flags_for_inode()). So remove nfsd_mode_check()'s WARN_ON_ONCE(). The nfserr_notdir return on that branch must stay. It guards the subsequent lookup_one_unlocked() -> __lookup_slow() path, which calls inode->i_op->lookup() with no NULL check, so returning nfserr_notdir is what keeps a client LOOKUP into such a @dentry from dereferencing a NULL method pointer.

CVSS: 8.2 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Received
Record last updated: Oct 19, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before ae251937c6f0237e5b555a5e4ba4595b8206e865; from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before e145e8d67a5d41c72d322e7f87ab474d39d9dfb7; from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before 9f4434893a2783f7384d993cea883aff3fb7a52d; from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before 2ef131323999539038e306773c8256403834361b; from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before b55b4d880bb080fa10eb08ba21a5d8679b8102fe; from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before 7ef182a8fe9c12b0d936880b1e504840639aa009; from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before a275de3bac5635514ca830f2e46b5ff0e66b5c4c; from e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c before aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e	CNA record

References

References

https://git.kernel.org/stable/c/ae251937c6f0237e5b555a5e4ba4595b8206e865
https://git.kernel.org/stable/c/e145e8d67a5d41c72d322e7f87ab474d39d9dfb7
https://git.kernel.org/stable/c/9f4434893a2783f7384d993cea883aff3fb7a52d
https://git.kernel.org/stable/c/2ef131323999539038e306773c8256403834361b
https://git.kernel.org/stable/c/b55b4d880bb080fa10eb08ba21a5d8679b8102fe
https://git.kernel.org/stable/c/7ef182a8fe9c12b0d936880b1e504840639aa009
https://git.kernel.org/stable/c/a275de3bac5635514ca830f2e46b5ff0e66b5c4c
https://git.kernel.org/stable/c/aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.