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CVE-2026-89704— nfsd: sample writeback error cursor before async COPY loop

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：在异步 COPY 循环开始前采样写回错误游标 原本在复制循环结束后才采样 到变量 “since” 中，随后在 返回后使用它通过 检测写回错误。 由于 nfsd_file 缓存对指向同一 inode 的多个请求复用同一个 对象，并发的 COMMIT 或稳定 WRITE（stable WRITE）在处理自身的 时，会通过 将 推进到当前的 。如果该推进操作恰好发生在“写回错误出现在 之后、COPY 工作线程采样 “since” 之前”，那么该工作线程捕获到的是已经

AI Predicted 5.5 Difficulty: Hard

Possible ATT&CK Techniques 1 AI

T1210 · Exploitation of Remote Services

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb< 52b2db7a72e19ac2686fa4b2a52406661e7bf9e2 affected
555dbf1a9aac6d3150c8b52fa35f768a692f4eeb< 8277d4a11ae2cb5495842be558fd946032c24363 affected
555dbf1a9aac6d3150c8b52fa35f768a692f4eeb< a1cbafe756cd5e6ab0e099062f37da7a5b081169 affected
555dbf1a9aac6d3150c8b52fa35f768a692f4eeb< 20a67a7d18221af736f124770c2c5e859b479046 affected
f14816f2f928c560d28ba344af689f56efcd6f55 affected
3145fe0ebb16e1715ad541a301bc6675c8375fcd affected
5.10.124< 5.11 affected
5.15.49< 5.16 affected
… +6 more rows
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I. Basic Information for CVE-2026-89704

Vulnerability Information
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Vulnerability Title
nfsd: sample writeback error cursor before async COPY loop
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: sample writeback error cursor before async COPY loop _nfsd_copy_file_range() samples dst->f_wb_err into "since" after the copy loop, then uses it to detect writeback errors via filemap_check_wb_err() once vfs_fsync_range() returns. Because the nfsd_file cache reuses a single struct file across requests targeting the same inode, a concurrent COMMIT or stable WRITE on dst advances dst->f_wb_err to the current mapping->wb_err via file_check_and_advance_wb_err() during its own vfs_fsync_range(). If that advancement lands between the writeback error appearing in mapping->wb_err and the COPY worker sampling "since", the worker captures the already-advanced cursor, errseq_check() sees cur == since and returns zero, and NFSD4_COPY_F_COMMITTED is set even though writeback failed. CB_OFFLOAD then encodes wr_stable_how = FILE_SYNC4, the client treats the copied data as durable, and the failure becomes silent data loss. Sample since once at the start of the function. The cursor then reflects state in effect before this COPY issues any writes, and filemap_check_wb_err() detects any error that occurs during the copy regardless of which thread first observes it. This matches the pattern used by nfsd_vfs_write() and nfsd4_clone_file_range().
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 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb ~ 52b2db7a72e19ac2686fa4b2a52406661e7bf9e2 -
Linux Linux 5.17 -

II. Public POCs for CVE-2026-89704

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III. Intelligence Information for CVE-2026-89704

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Patches & Fixes for CVE-2026-89704 (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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