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CVE-2026-72170— 9p: skip nlink update in cacheless mode to fix WARN_ON

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.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于v9fs_dec_count()函数无条件调用drop_nlink()，在无缓存模式下引发竞争条件，可能导致内核触发警告。

CVSS 7.8 · High EPSS 0.16% · P6

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux ac89b2ef9b55924bcf922251f043ba73a32d05bb< 6086469f7d469549bfd070348b717a6e43736200 affected
ac89b2ef9b55924bcf922251f043ba73a32d05bb< ab257019cb72f467b55c95384d99c94e3908b928 affected
ac89b2ef9b55924bcf922251f043ba73a32d05bb< 4ec4ebe40c82cb4c60756732f6593055d010c59c affected
ac89b2ef9b55924bcf922251f043ba73a32d05bb< a5a682b016ef5b5384e28f6d652d47a8f8e73d37 affected
ac89b2ef9b55924bcf922251f043ba73a32d05bb< de79c3f3643841b8659a71958df7cf2a66bfd409 affected
ac89b2ef9b55924bcf922251f043ba73a32d05bb< 8d610017c992de705b304d3d727a6e3a86af6149 affected
ac89b2ef9b55924bcf922251f043ba73a32d05bb< 8faccac11e1369adddf5d80f4a45af93f13b2e1a affected
ac89b2ef9b55924bcf922251f043ba73a32d05bb< 574aa0b4799470ac814479f1138d19efe6262255 affected
… +10 more rows
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I. Basic Information for CVE-2026-72170

Vulnerability Information
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Vulnerability Title
9p: skip nlink update in cacheless mode to fix WARN_ON
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: 9p: skip nlink update in cacheless mode to fix WARN_ON v9fs_dec_count() unconditionally calls drop_nlink() on regular files, even when the inode's nlink is already zero. In cacheless mode the client refetches inode metadata from the server (the source of truth) on every operation, so by the time v9fs_remove() returns, the locally cached nlink may already reflect the post-unlink value: 1. Client initiates unlink, server processes it and sets nlink to 0 2. Client refetches inode metadata (nlink=0) before unlink returns 3. Client's v9fs_remove() completes successfully 4. Client calls v9fs_dec_count() which calls drop_nlink() on nlink=0 This race is easily triggered under heavy unlink workloads, such as stress-ng's unlink stressor, producing the following warning: WARNING: fs/inode.c:417 at drop_nlink+0x4c/0xc8 Call trace: drop_nlink+0x4c/0xc8 v9fs_remove+0x1e0/0x250 [9p] v9fs_vfs_unlink+0x20/0x38 [9p] vfs_unlink+0x13c/0x258 ... In cacheless mode the server is authoritative and the inode is on its way out, so locally adjusting nlink buys nothing. Skip v9fs_dec_count() entirely when neither CACHE_META nor CACHE_LOOSE is set, which both avoids the warning and removes a class of nlink races (two concurrent unlinkers observing nlink > 0 and both calling drop_nlink()) that an nlink == 0 guard alone would only narrow rather than close.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于v9fs_dec_count()函数无条件调用drop_nlink()，在无缓存模式下引发竞争条件，可能导致内核触发警告。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux ac89b2ef9b55924bcf922251f043ba73a32d05bb ~ 6086469f7d469549bfd070348b717a6e43736200 -
Linux Linux 4.17 -

II. Public POCs for CVE-2026-72170

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III. Intelligence Information for CVE-2026-72170

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Patches & Fixes for CVE-2026-72170 (8)

Same Patch Batch · Linux · 2026-08-15 · 845 CVEs total

CVE-2026-74475 10.0 CRITICAL vxlan: use neigh_ha_snapshot() in route_shortcircuit()
CVE-2026-74280 10.0 CRITICAL crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
CVE-2026-72407 10.0 CRITICAL geneve: validate inner network offset in geneve_gro_complete()
CVE-2026-72408 10.0 CRITICAL geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
CVE-2026-72421 10.0 CRITICAL ipv4: fib: Don't ignore error route in local/main tables.
CVE-2026-74309 10.0 CRITICAL vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
CVE-2026-74279 10.0 CRITICAL crypto: cavium/cpt - fix DMA cleanup using wrong loop index
CVE-2026-72493 9.9 CRITICAL net: serialize netif_running() check in enqueue_to_backlog()
CVE-2026-72381 9.8 CRITICAL ksmbd: fix use-after-free of fp->owner.name in durable handle owner check
CVE-2026-72393 9.8 CRITICAL eth: fbnic: don't cache shinfo across skb realloc
CVE-2026-74401 9.8 CRITICAL dlm: fix add msg handle in send_queue ordered
CVE-2026-74406 9.8 CRITICAL vxlan: Fix potential null-ptr-deref in vxlan_gro_prepare_receive().
CVE-2026-72355 9.8 CRITICAL netfs: Fix barriering when walking subrequest list
CVE-2026-72339 9.8 CRITICAL qede: fix off-by-one in BD ring consumption on build_skb failure
CVE-2026-72211 9.8 CRITICAL ntfs: grow index root value before reparent header update
CVE-2026-72194 9.8 CRITICAL fs/ntfs3: add depth limit to indx_find_buffer to prevent stack overflow
CVE-2026-72351 9.8 CRITICAL gue: validate REMCSUM private option length
CVE-2026-72366 9.8 CRITICAL netfs: Fix netfs_create_write_req() to handle async cache object creation
CVE-2026-72098 9.8 CRITICAL dm-verity: fix buffer overflow in FEC calculation
CVE-2026-72083 9.8 CRITICAL scsi: target: core: Fix iSCSI ISID use-after-free in REGISTER AND MOVE

Showing top 20 of 845 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-72170

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