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CVE-2026-89713— NFSD: check truncate permission under inode 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，已修复以下漏洞： NFSD：在 inode 锁保护下检查截断权限 在获取 之前，会检查尺寸更新是否需要 权限。该检查所依据的文件大小是通过一次未加锁的读取操作获取的，而实际的 更新则是在后续持有 的情况下，由 应用的。 这为仅追加（append-only）文件留下了一个 TOCTOU（检查时间与使用时间） 窗口。如果在未加锁采样时客户端发送的 不会缩小文件，但在 获取 之前，可能有并发的追加操作延长了文件。此时 执行一次真正的截断操作，却未进行 检查来拒绝 。由于 VFS 中的 trunca

AI Predicted 5.5 Difficulty: Hard

Possible ATT&CK Techniques 2 AI

T1208 T1625

Affected Version Matrix 20

VendorProduct Version RangeStatus
Linux Linux 783112f7401ff449d979530209b3f6c2594fdb4e< 3afa17d93ba8c925f49370c816c6dae5112d8c24 affected
783112f7401ff449d979530209b3f6c2594fdb4e< d8352da196349182e1afd5a93308256cddc0a97d affected
783112f7401ff449d979530209b3f6c2594fdb4e< 44086254479035de42ca3d286ecf25521d4e6325 affected
783112f7401ff449d979530209b3f6c2594fdb4e< b778e0e0a16759f22a70579c3cf8d254a40d4a7f affected
604a3c407026d6162d15300478e63f901e435efc affected
cc4d5dc73841b98d33cdfb9822d70b0aac4beca5 affected
3ee4f442e5b37a537297b812557b1163f96b5399 affected
a3c6cbc4eac4473ed5461d5faae2794d3e5c0e44 affected
… +12 more rows
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I. Basic Information for CVE-2026-89713

Vulnerability Information
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Vulnerability Title
NFSD: check truncate permission under inode lock
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: NFSD: check truncate permission under inode lock nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC before it takes inode_lock(). The comparison uses the file size sampled by that unlocked read, but the actual ATTR_SIZE update is applied later under inode_lock() by notify_change(). This leaves a TOCTOU window for append-only files. If a client sends a SETATTR that does not shrink the file at the time of the unlocked sample, a concurrent append can extend the file before nfsd_setattr() takes inode_lock(). notify_change() then applies a real truncation without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS truncate syscall paths perform their own append-only checks before calling notify_change(), so NFSD must make this decision against the locked size it is about to change. Split the write-count acquisition from the truncation permission check. Keep get_write_access() before the locked setattr work, then recheck whether the requested size is below i_size_read(inode) after inode_lock() has been acquired and before notify_change(ATTR_SIZE). This also avoids the plain unlocked inode->i_size load.
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 783112f7401ff449d979530209b3f6c2594fdb4e ~ 3afa17d93ba8c925f49370c816c6dae5112d8c24 -
Linux Linux 4.11 -

II. Public POCs for CVE-2026-89713

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III. Intelligence Information for CVE-2026-89713

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Patches & Fixes for CVE-2026-89713 (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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