Linux KernelOperating system · Linux
CVE-2026-43376
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free by using call_rcu() for oplock_info ksmbd currently frees oplock_info immediately using kfree(), even though it is accessed under RCU read-side critical sections in places like opinfo_get() and proc_show_files(). Since there is no RCU grace period delay between nullifying the pointer and freeing the memory, a reader can still access oplock_info structure after it has been freed. This can leads to a use-after-free especially in opinfo_get() where atomic_inc_not_zero() is called on already freed memory. Fix this by switching to deferred freeing using call_rcu().
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceUse-after-free vulnerability in Linux kernel's ksmbd where oplock_info structures are freed immediately with kfree() while still being accessed under RCU read-side critical sections in functions like opinfo_get() and proc_show_files(). Without an RCU grace period delay, readers can access freed memory, particularly dangerous when atomic_inc_not_zero() is called on deallocated structures.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 6.6.88, < 6.6.130>= 6.12.25, < 6.12.78>= 6.14.4, < 6.15>= 6.15.1, < 6.18.19>= 6.19, < 6.19.9= 6.15= 7.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check kernel versionRun 'uname -r' to get the running kernel versionAffected if The version falls within any of these ranges: 6.6.88 to 6.6.129, 6.12.25 to 6.12.77, 6.14.4 to 6.14.x (before 6.15), 6.15.x (including 6.15 and 6.15.1+), 6.16-6.18.18, or 6.19.0-6.19.8, or 7.0.x
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Verify ksmbd is enabledCheck if ksmbd kernel module is loaded: 'lsmod | grep ksmbd' or check kernel config for CONFIG_KSMBD=y or CONFIG_KSMBD=mAffected if ksmbd module is loaded or built into the kernel
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Confirm SMB server functionality is activeCheck for ksmbd server process: 'ps aux | grep ksmbd' or check for /proc/fs/ksmbd/ mount pointAffected if ksmbd is actively serving SMB shares (oplock_info structures are being allocated)
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Check for oplock usageInspect /proc/fs/ksmbd/conn.list or /proc/fs/ksmbd/share.list for active connections (oplock_info structures exist when SMB connections with oplocks are active)Affected if There are active SMB connections using oplocks (oplock_info structures are in use and potentially vulnerable)
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Identify specific vulnerable code pathsReview ksmbd source for opinfo_get() and proc_show_files() functions; verify they use atomic_inc_not_zero() on oplock_info structures without proper RCU grace period handlingAffected if The ksmbd implementation contains the vulnerable pattern of immediate kfree() on oplock_info structures accessed under RCU read-side critical sections
You are affected if you run a vulnerable kernel version AND have ksmbd enabled with active SMB connections using oplocks, as the use-after-free occurs when oplock_info structures are freed without RCU grace period delay while still being accessed.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped6.6.1306.12.786.15
Apply the kernel patch that replaces immediate kfree() with deferred call_rcu() freeing for oplock_info structures, ensuring RCU grace periods elapse before memory is released.
Linux Kernel 6.6.130 / 6.12.78 / 6.15 / 6.18.19 (depending on your current branch)
- Identify the currently running Linux kernel version using `uname -r`
- Determine which version range your current kernel falls into based on the affected versions: 6.6.88-6.6.129, 6.12.25-6.12.77, 6.14.4-6.14.x, or 6.15.1-6.18.18
- Upgrade the Linux kernel to a version that includes the fix. The fix was applied via commit 08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c
- For kernel 6.6.x, upgrade to version 6.6.130 or later
- For kernel 6.12.x, upgrade to version 6.12.78 or later
- For kernel 6.14.x, upgrade to version 6.15 or later
- For kernel 6.15.x, upgrade to version 6.18.19 or later
- Reboot the system to load the patched kernel
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-43376 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-43376 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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