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CVE-2026-89712— NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

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：在释放 nfsd_ssc_lock 后重启 ssc_expire_umount 遍历 使用 遍历 。对于每个过期的条目，它会设置 ，然后释放 以执行源 vfsmount 上的 ，随后重新获取锁，对条目执行 + ，并通过宏保存的 指针继续遍历。 标志在锁释放期间保护当前 免受并发 查找者的干扰，但它并未固定（pin） 。另一个 NFSd RPC 线程若在其源服务器挂载失败并到达 ，则会在同一窗口内获取 ，对其自身的 条目执行 + ，然后释放锁。如果该条目恰好是过

AI Predicted 5.5 Difficulty: Hard

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux f4e44b393389c77958f7c58bf4415032b4cda15b< 77de363d9a1c8cd35f20482782c612cda085791a affected
f4e44b393389c77958f7c58bf4415032b4cda15b< 4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8 affected
f4e44b393389c77958f7c58bf4415032b4cda15b< 7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9 affected
f4e44b393389c77958f7c58bf4415032b4cda15b< 036c1b182f4da65363e79ec0ac276edc6b7296e5 affected
a4bc287943f5695209ff36bdc89f17b48d68fae7 affected
5.10.220< 5.11 affected
5.14 affected
< 5.14 unaffected
… +4 more rows
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I. Basic Information for CVE-2026-89712

Vulnerability Information
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Vulnerability Title
NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with list_for_each_entry_safe(ni, tmp, ...). For each expired entry it sets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the source vfsmount, then reacquires the lock to list_del + kfree the entry and continue iterating via the macro's saved tmp pointer. The nsui_busy flag protects the current ni from concurrent nfsd4_ssc_setup_dul() finders during the lock-drop window, but it does not pin tmp. Another nfsd RPC thread that fails its source- server mount and reaches nfsd4_ssc_cancel_dul() will, during that same window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount item, and release the lock. If that item is the saved tmp of the expire walk, the next iteration dereferences a freed nfsd4_ssc_umount_item. Restart the walk from the head after the mntput() unlock window so no saved next pointer survives the lock-drop. The list is bounded by the number of active inter-server source mounts (typically small) and the expire delayed-work runs periodically rather than per-IO, so the restart is cheap.
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 f4e44b393389c77958f7c58bf4415032b4cda15b ~ 77de363d9a1c8cd35f20482782c612cda085791a -
Linux Linux 5.14 -

II. Public POCs for CVE-2026-89712

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III. Intelligence Information for CVE-2026-89712

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Other References for CVE-2026-89712 (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

V. Comments for CVE-2026-89712

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