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Codeready Linux Builder EusApplication · Redhat

CVE-2023-6356

HIGH · 7.5 CVSS v3.1 Published 2024-02-07
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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
A flaw was found in the Linux kernel's NVMe driver. This issue may allow an unauthenticated malicious actor to send a set of crafted TCP packages when using NVMe over TCP, leading the NVMe driver to a NULL pointer dereference in the NVMe driver and causing kernel panic and a denial of service.

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 confidence

A NULL pointer dereference vulnerability exists in the Linux kernel's NVMe driver when using NVMe over TCP. An unauthenticated remote attacker can send crafted TCP packets to trigger the NULL pointer dereference, causing kernel panic and resulting in denial of service.

MitigationApply the Linux kernel security update that addresses this vulnerability. As a temporary workaround, restrict network access to NVMe over TCP ports or disable NVMe over TCP 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
Codeready Linux Builder EusApplication
Affected:= 8.6= 9.2
Codeready Linux Builder Eus For Power Little Endian EusApplication
Affected:= 8.6_ppc64le= 9.2_ppc64le
Codeready Linux Builder For Arm64 EusApplication
Affected:= 8.6_aarch64= 9.2_aarch64
Codeready Linux Builder For Ibm Z Systems EusApplication
Affected:= 9.2_s390x
Enterprise LinuxOperating system
Affected:= 8.0= 9.0
Enterprise Linux EusOperating system
Affected:= 8.6= 9.2
Enterprise Linux For Arm 64 EusOperating system
Affected:= 8.6_aarch64= 9.2_aarch64
Enterprise Linux For Ibm Z Systems EusOperating system
Affected:= 8.6_s390x= 9.2_s390x

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 if NVMe-TCP kernel module is loaded
    Run 'lsmod | grep nvmet' or 'lsmod | grep nvme' to see if the NVMe over TCP modules are currently loaded in memory
    Affected if The module is loaded and the kernel version is within the affected range (8.0-8.6 or 9.0-9.2 for RHEL)
  2. Identify active NVMe over TCP connections or listeners
    Check for active NVMe-TCP sessions using 'nvme list' or inspect network listening ports for 4420/tcp (NVMe-TCP default port). Use 'ss -tlnp | grep 4420' or 'netstat -tlnp | grep 4420'
    Affected if NVMe over TCP connections or listeners are active on the system
  3. Verify kernel version matches affected Red Hat releases
    Run 'uname -r' to get the running kernel version and compare against affected RHEL versions: 8.0-8.6 or 9.0-9.2. For architecture-specific variants, also confirm the system architecture (aarch64, ppc64le, s390x)
    Affected if Kernel version falls within the affected RHEL version range (8.x or 9.x)
  4. Confirm NVMe over Fabrics configuration exists
    Check for NVMe over TCP configuration in /etc/nvme/ or review 'nvme list-subsys' output to see if any NVMe over Fabrics targets or controllers are configured
    Affected if NVMe over TCP subsystems or controllers are configured and active

The system is affected if NVMe over TCP is actively used (module loaded with active connections) AND the kernel version is within the Red Hat Enterprise Linux 8.0-8.6 or 9.0-9.2 range listed in the affected products.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Linux kernel security update that addresses this vulnerability. As a temporary workaround, restrict network access to NVMe over TCP ports or disable NVMe over TCP if not required.

Fix this in Codeready Linux Builder Eus Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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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-2023-6356 in production — separate from our analysis above.

No notes yet

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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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data