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

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： NFSD：从 中移除存在缺陷的 提交 （"nfsd: 在目录的 中检查 ”）的提交说明中详细描述了当时认为合理的假设，该假设促使在 中添加了 。然而，这一假设在 NFS 再导出（reexport）场景下并不成立。 当 NFSD 导出一个 NFS 文件系统时， 遇到的 可能没有 （参见 中对 和 的处理，以及 ）。 因此，应当移除 中的 。该分支中返回 的逻辑必须保留。它保护了后续 → 的调用路径。该路径会调用 ，且没有对函数指针进行空值检查。因此，返回 可以防止客户端对

AI Predicted 4.4 Difficulty: Theoretical

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c< b55b4d880bb080fa10eb08ba21a5d8679b8102fe affected
e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c< 7ef182a8fe9c12b0d936880b1e504840639aa009 affected
e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c< a275de3bac5635514ca830f2e46b5ff0e66b5c4c affected
e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c< aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e affected
4.8 affected
< 4.8 unaffected
6.12.109≤ 6.12.* unaffected
6.18.50≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-89711

Vulnerability Information
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Vulnerability Title
NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c ~ b55b4d880bb080fa10eb08ba21a5d8679b8102fe -
Linux Linux 4.8 -

II. Public POCs for CVE-2026-89711

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III. Intelligence Information for CVE-2026-89711

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Patches & Fixes for CVE-2026-89711 (4)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89491 ocfs2: cluster: don't sleep while holding o2hb_live_lock in o2hb_region_pin()
CVE-2026-89477 sctp: fix NULL deref on untransmitted RECONF completion
CVE-2026-89478 sctp: drop a chunk if its transport was removed
CVE-2026-89479 sctp: stop processing a packet once its association is deleted
CVE-2026-89480 nvme-tcp: reject a read that transferred too few bytes
CVE-2026-89482 nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89481 nvme-tcp: fix host memory disclosure on R2T for a read command
CVE-2026-89483 nvme: zero the discard fallback page
CVE-2026-89484 lockd: fix NULL dereference on lockowner allocation failure
CVE-2026-89485 lockd: pin next file across nlm_inspect_file lock-drop
CVE-2026-89486 ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user()
CVE-2026-89487 openvswitch: only skb_tx_error() a packet we are about to drop
CVE-2026-89488 openvswitch: Fix CT limit teardown use-after-free
CVE-2026-89489 openrisc: fix arbitrary kernel memory access via or1k_atomic syscall
CVE-2026-89500 ring-buffer: Make cpu_buffer::free_page a buffer_data_read_page
CVE-2026-89497 orangefs: skip leading spaces before parsing client debug masks
CVE-2026-89498 orangefs: fix double-free of trailer_buf on readdir copy failure
CVE-2026-89499 ring-buffer: Stop remote reader update when page swap fails
CVE-2026-89496 ocfs2: always run deallocs on copy-on-write completion
CVE-2026-89501 ring-buffer: Hold cpu_buffer::lock when resizing a subbuf

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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