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VulnerabilityPublished Updated

CVE-2026-97557: Linux kernel · smb: client: avoid leaking refcount in cifs_queue_oplock_break()

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.5 High · fixed in dfe7b750c7e069873a8a57a11c816831a235618a : patch Linux kernel soon.

Data as of 26 Oct 2026, 12:55 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in dfe7b750c7e069873a8a57a11c816831a235618a, de2a6bcff2659bea40c7485115b57f0ae189fc01, af0193bbf1ac8c0f67f972998b0cc629d6116cf6 +8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • >=3.16.72 <3.17
  • >=4.9.171 <4.10
  • >=4.14.114 <4.15
  • >=4.19.37 <4.20
  • >=5.0.10 <5.1
Fixed in
  • dfe7b750c7e069873a8a57a11c816831a235618a
  • de2a6bcff2659bea40c7485115b57f0ae189fc01
  • af0193bbf1ac8c0f67f972998b0cc629d6116cf6
  • 735a3a610136ae10f381d0909dff38e5b5c5f056
  • 9f2e63f1b2d5fc5b5423424902c091123e220e7e
  • 5.1
  • 4.20
  • 4.15
  • 4.10
  • 3.17
  • 2ed2c29dd9593637cfa25ac1eb23241b20202778
LinuxLinuxAffected
  • =5.1
Fixed in–

AI-suggested

This vulnerability has been fixed in Linux kernel versions 3.17, 4.10, 4.15, 4.20, 5.1, and corresponding commit versions. Users should upgrade to these fixed versions or later to remediate the issue. No other mitigations are required as the fix addresses the root cause of the reference count leak.

Description

CVE-2026-97557 is a vulnerability in the Linux kernel's SMB client implementation related to reference count leakage in the cifs_queue_oplock_break() function. The flaw occurs because the function increments a file reference count before queueing a work item, but if a second oplock break arrives while the first work is still queued, the second work is not queued and the reference count is leaked. This leak can cause unmount operations for the CIFS filesystem to fail, resulting in kernel bugs and busy inode errors. The issue is fixed by only incrementing the reference count after successfully queueing the work item.

References

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