CVE-2026-97557: Linux kernel · smb: client: avoid leaking refcount in cifs_queue_oplock_break()
Affects Linux kernelSource CVE Database V5
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
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| 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
- git.kernel.org/stable/c/735a3a610136ae10f381d0909dff38e5b5c5f056 (opens in a new tab)
- git.kernel.org/stable/c/de2a6bcff2659bea40c7485115b57f0ae189fc01 (opens in a new tab)
- git.kernel.org/stable/c/af0193bbf1ac8c0f67f972998b0cc629d6116cf6 (opens in a new tab)
- git.kernel.org/stable/c/2ed2c29dd9593637cfa25ac1eb23241b20202778 (opens in a new tab)
- git.kernel.org/stable/c/dfe7b750c7e069873a8a57a11c816831a235618a (opens in a new tab)
- git.kernel.org/stable/c/9f2e63f1b2d5fc5b5423424902c091123e220e7e (opens in a new tab)