CVE-2026-72170

Kernel inode corruption via cacheless 9p unlink race

Published Aug 15, 2026 · Updated Aug 15, 2026

Race condition in Linux kernel 9p clients allows local users to corrupt inode link counts through concurrent unlink operations. In cacheless mode, v9fs_dec_count() calls drop_nlink() after refreshed server metadata has already set the inode link count to zero. Exploitation requires write access to an already-mounted cacheless 9p filesystem; each hit emits a kernel warning and underflows inode link accounting, while panic_on_warn turns the warning into a kernel crash.

CVSS severity7.8
High
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Linux kernel 9p clients allows local users to corrupt inode link counts through concurrent unlink operations. In cacheless mode, v9fs_dec_count() calls drop_nlink() after refreshed server metadata has already set the inode link count to zero. Exploitation requires write access to an already-mounted cacheless 9p filesystem; each hit emits a kernel warning and underflows inode link accounting, while panic_on_warn turns the warning into a kernel crash.

The record

CVE
CVE-2026-72170
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.17
  2. Affected versionversion=ac89b2ef9b55924bcf922251f043ba73a32d05bb <574aa0b4799470ac814479f1138d19efe6262255
  3. Affected versionversion=ac89b2ef9b55924bcf922251f043ba73a32d05bb <8d610017c992de705b304d3d727a6e3a86af6149
  4. Affected versionversion=ac89b2ef9b55924bcf922251f043ba73a32d05bb <8faccac11e1369adddf5d80f4a45af93f13b2e1a
  5. Affected versionversion=ac89b2ef9b55924bcf922251f043ba73a32d05bb <a5a682b016ef5b5384e28f6d652d47a8f8e73d37
  6. Affected versionversion=ac89b2ef9b55924bcf922251f043ba73a32d05bb <de79c3f3643841b8659a71958df7cf2a66bfd409

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=4.17; version=ac89b2ef9b55924bcf922251f043ba73a32d05bb <574aa0b4799470ac814479f1138d19efe6262255; version=ac89b2ef9b55924bcf922251f043ba73a32d05bb <8d610017c992de705b304d3d727a6e3a86af6149; version=ac89b2ef9b55924bcf922251f043ba73a32d05bb <8faccac11e1369adddf5d80f4a45af93f13b2e1a; version=ac89b2ef9b55924bcf922251f043ba73a32d05bb <a5a682b016ef5b5384e28f6d652d47a8f8e73d37; version=ac89b2ef9b55924bcf922251f043ba73a32d05bb <de79c3f3643841b8659a71958df7cf2a66bfd409

Published CVSS scores

7.8Linux Kernel CVE TeamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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