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Linux KernelOperating system · Linux

CVE-2026-31536

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-24
Fix available
A fix is available. Upgrade to 6.18.11 / 6.19.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

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 · unedited
In the Linux kernel, the following vulnerability has been resolved: smb: server: let send_done handle a completion without IB_SEND_SIGNALED With smbdirect_send_batch processing we likely have requests without IB_SEND_SIGNALED, which will be destroyed in the final request that has IB_SEND_SIGNALED set. If the connection is broken all requests are signaled even without explicit IB_SEND_SIGNALED.

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 confidence

This is a kernel-level vulnerability in the Linux SMB server (smbdirect/RDMA) implementation. The issue is in the send_done handler which fails to properly handle completions when IB_SEND_SIGNALED flag is not set. During batch processing, requests without IB_SEND_SIGNALED are destroyed only when the final request with IB_SEND_SIGNALED completes, but if the connection breaks, all requests get signaled unexpectedly. This can lead to memory corruption, use-after-free, or improper cleanup of in-flight SMB direct operations.

MitigationApply the kernel patch that modifies send_done to properly handle completions without IB_SEND_SIGNALED, then update to the patched kernel version. Until patched, consider disabling SMB direct (RDMA) functionality if not required.

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
Affected:>= 5.15, < 6.18.11>= 6.19, < 6.19.1

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Check the running kernel version
    Run `uname -r` or `cat /proc/version` to obtain the kernel version
    Affected if The version is >= 5.15 and < 6.18.11, OR >= 6.19 and < 6.19.1
  2. Verify if SMB direct/RDMA is enabled in the kernel
    Run `lsmod | grep -E 'rdma|smbdirect' ` to see if RDMA or smbdirect modules are loaded, or check `/sys/module/smbdirect/parameters/enabled` if the module exists
    Affected if The smbdirect or rdma kernel modules are loaded into memory
  3. Check if SMB direct is configured in smb.conf
    Examine `/etc/samba/smb.conf` for the 'rdma' parameter under the [global] or share sections, typically appearing as `rdma = yes` or `smbdirect = yes`
    Affected if SMB direct or RDMA is explicitly enabled in the Samba configuration file
  4. Check for active RDMA connections
    Run `rdma stat` or examine `/sys/class/infiniband/` to see if there are any active RDMA interfaces that could be used for SMB direct
    Affected if RDMA interfaces are present and active on the system
  5. Identify if SMB over RDMA is in use
    Use `netstat -anp | grep 445` or check SMB logs to look for connections indicating RDMA transport, or examine `/proc/fs/cifs/Stats` if CIFS is used
    Affected if SMB traffic is using RDMA transport (visible as rds or rdma in connection details)

A system is affected only if it runs a vulnerable kernel version AND has SMB direct/RDMA functionality enabled and actively in use.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 6.18.11 / 6.19.1 or later
Fixed in 6.18.116.19.1
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that modifies send_done to properly handle completions without IB_SEND_SIGNALED, then update to the patched kernel version. Until patched, consider disabling SMB direct (RDMA) functionality if not required.

Recommended fix High confidence

6.18.11 or later for 6.18.x branch; 6.19.1 or later for 6.19.x branch

  1. 1. Identify the current kernel version using 'uname -r' or 'cat /proc/version'
  2. 2. For systems running kernel >= 5.15 and < 6.18.11: Upgrade to kernel version 6.18.11 or later (e.g., 6.18.x latest stable)
  3. 3. For systems running kernel >= 6.19 and < 6.19.1: Upgrade to kernel version 6.19.1 or later (e.g., 6.19.x latest stable)
  4. 4. Use your distribution's package manager to install the new kernel (e.g., 'apt update && apt upgrade' for Debian/Ubuntu, 'yum update' for RHEL/CentOS, or 'pacman -Syu' for Arch)
  5. 5. After installation, reboot the system to load the fixed kernel
  6. 6. Verify the new kernel version is running with 'uname -r'
Caveat Kernel upgrades may require driver/compatibility verification; ensure critical modules and custom drivers are compatible with the target version

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
15.0 hours of engineering $2,560
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-31536 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data