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CVE-2026-89689— nfsd: don't free session slots that are still in use

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，已修复以下漏洞： nfsd：不要释放仍在使用中的会话槽位 可能会释放其当前正在处理的那个槽位。 当会话收缩器将 降低到低于 时，收缩路径在调用 之前会检查三个条件： 1. （收缩已被通告） 2. （槽位是最新的） 3. （客户端已确认） 然而， 从未与 进行比较。 一个在范围 内使用槽位的客户端，可以满足上述所有三个条件：其槽位具有当前世代（由先前的 SEQUENCE 设置），并且它发送 以确认缩减。 随后， 会释放所有索引 >= 的槽位，包括调用者自己的槽位。该函数继续写入 、 和 ，并将

AI Predicted 7.5 Difficulty: Moderate

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7< 72d40b103bb03f0124d3a3c8f71a30cbafaf6afa affected
fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7< b449b134e7762ddf98653a4b1d3e76d2d212ea64 affected
fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7< f5d22e372f4ac3eb287037a488c29691d52a6330 affected
6.14 affected
< 6.14 unaffected
6.18.50≤ 6.18.* unaffected
7.2.4≤ 7.2.* unaffected
7.3-rc1≤ * unaffected
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I. Basic Information for CVE-2026-89689

Vulnerability Information
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Vulnerability Title
nfsd: don't free session slots that are still in use
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: don't free session slots that are still in use nfsd4_sequence() can free the very slot it is currently processing. When the session shrinker has reduced se_target_maxslots below se_fchannel.maxreqs, the shrink path checks three conditions before calling free_session_slots(): 1. se_target_maxslots < maxreqs (shrink was advertised) 2. slot->sl_generation == se_slot_gen (slot is up-to-date) 3. seq->maxslots <= se_target_maxslots (client acknowledges) However, seq->slotid is never checked against se_target_maxslots. A client using a slot in the range [se_target_maxslots, maxreqs) can satisfy all three conditions: its slot has the current generation (set by a prior SEQUENCE), and it sends sa_highest_slotid <= se_target_maxslots to acknowledge the reduction. free_session_slots() then kfrees every slot at index >= se_target_maxslots, including the caller's own slot. The function continues to write sl_seqid, sl_flags, sl_generation, and stores the dangling pointer in cstate->slot. Later, nfsd4_store_cache_entry() copies up to maxresp_cached bytes of the compound reply into the freed sl_data[] array, corrupting whatever slab object now occupies that address. Additionally, a concurrent thread processing SEQUENCE on a different high-numbered slot can have its slot freed out from under it. NFSD4_SLOT_INUSE is set under nn->client_lock before the lock is released, so any concurrent thread past SEQUENCE will have its slot marked. However, free_session_slots() does not check NFSD4_SLOT_INUSE before freeing. Fix both problems by: 1. Checking that the current request's slotid is below the shrink boundary. 2. Scanning slots in the to-be-freed range for NFSD4_SLOT_INUSE and deferring the shrink if any are active.
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 fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7 ~ 72d40b103bb03f0124d3a3c8f71a30cbafaf6afa -
Linux Linux 6.14 -

II. Public POCs for CVE-2026-89689

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III. Intelligence Information for CVE-2026-89689

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Patches & Fixes for CVE-2026-89689 (3)

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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