Linux KernelOperating system · Linux
CVE-2026-31608
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: smb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list() smb_direct_flush_send_list() already calls smb_direct_free_sendmsg(), so we should not call it again after post_sendmsg() moved it to the batch list.
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 · moderate confidenceA double-free vulnerability exists in the Linux kernel's SMB server implementation where smb_direct_free_sendmsg() is called both within smb_direct_flush_send_list() and again after post_sendmsg(), causing a use-after-free condition that could be exploited for privilege escalation or denial of service.
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
< 6.18.24>= 6.19, < 6.19.14>= 7.0, < 7.0.1CVSS 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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Verify smb_direct module is in useRun 'lsmod | grep smb_direct' to see if the smb_direct kernel module is loaded. Also check 'cat /proc/modules | grep smb_direct'.Affected if The smb_direct module is loaded or compiled into the kernel (the double-free can only trigger when this module handles SMB direct traffic).
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Check running kernel versionRun 'uname -r' to get the exact kernel version string, or 'cat /proc/version' for more details.Affected if The kernel version falls within any of these ranges: < 6.18.24, >= 6.19 but < 6.19.14, or >= 7.0 but < 7.0.1.
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Confirm SMB direct functionality is enabledCheck kernel config with 'cat /boot/config-$(uname -r) | grep -i smb' or check if ksmbd daemon (kernel SMB server) is running with 'ps aux | grep ksmbd', as this vulnerability affects the in-kernel SMB server.Affected if The ksmbd daemon is active or the smb_direct module is actively handling SMB connections (the vulnerable code path only executes during SMB direct send operations).
If the kernel version is within the affected ranges AND the smb_direct module is loaded or ksmbd is running, the environment is vulnerable to this double-free flaw.
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 · scoped6.18.246.19.147.0.1
Apply the Linux kernel patch that removes the redundant smb_direct_free_sendmsg() call after smb_direct_flush_send_list(), typically delivered through kernel security updates.
6.18.24 (for 6.18.x branch), 6.19.14 (for 6.19.x branch), or 7.0.1 (for 7.0.x branch)
- 1. Check current kernel version using: uname -r
- 2. Determine which version branch your kernel belongs to (6.18.x, 6.19.x, or 7.0.x)
- 3. For kernels < 6.18.24: upgrade to kernel version 6.18.24 or later
- 4. For kernels >= 6.19 and < 6.19.14: upgrade to kernel version 6.19.14 or later
- 5. For kernels >= 7.0 and < 7.0.1: upgrade to kernel version 7.0.1 or later
- 6. Reboot the system to apply the new kernel
- 7. Verify the fix is applied by checking the kernel version with: uname -r
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
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-31608 — 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-2026-31608 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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