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StorageApplication · Redhat

CVE-2023-3347

MEDIUM · 5.9 CVSS v3.1 Published 2023-07-20
Fix available
A fix is available. Upgrade to 4.17.10 / 4.18.5 or later.
See remediation →
68/100
Remediation priority · Elevated
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 vulnerability was found in Samba's SMB2 packet signing mechanism. The SMB2 packet signing is not enforced if an admin configured "server signing = required" or for SMB2 connections to Domain Controllers where SMB2 packet signing is mandatory. This flaw allows an attacker to perform attacks, such as a man-in-the-middle attack, by intercepting the network traffic and modifying the SMB2 messages between client and server, affecting the integrity of the data.

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

A flaw in Samba's SMB2 packet signing implementation allows the signing requirement to be bypassed even when 'server signing = required' is configured or when connecting to Domain Controllers where signing is mandatory. An attacker performing a man-in-the-middle attack can intercept and modify SMB2 messages without detection, compromising data integrity.

MitigationEnsure Samba installations are updated to versions that enforce SMB2 packet signing as specified in configuration. Verify that 'server signing = required' is properly enforced and monitor for configuration drift.

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
StorageApplication
Affected:= 3.0
Enterprise LinuxOperating system
Affected:= 8.0= 9.0
FedoraOperating system
Affected:= 38
SambaApplication
Affected:>= 4.17.0, < 4.17.10>= 4.18.0, < 4.18.5

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

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 installed Samba version
    Run 'smbstatus --version' or 'rpm -q samba' to obtain the Samba version number
    Affected if The version is >= 4.17.0 and < 4.17.10, or >= 4.18.0 and < 4.18.5
  2. Locate smb.conf configuration file
    Run 'testparm -s' or check '/etc/samba/smb.conf' (path may vary by OS) to view the Samba configuration
    Affected if The file exists and contains 'server signing = required' or the server is configured as a Domain Controller (role = active directory domain controller)
  3. Verify SMB signing enforcement in configuration
    Search the smb.conf output for the 'server signing' parameter using 'testparm -s 2>/dev/null | grep -i signing'
    Affected if The parameter is set to 'required' (the vulnerability allows bypass even when this is set)
  4. Check if server is configured as Domain Controller
    Search the smb.conf output for 'role' or 'server role' parameter, or check for 'domain controller' in the configuration
    Affected if The server role includes 'active directory domain controller' or 'domain controller' (signing is mandatory for DC connections but can be bypassed in this version)

You are affected if Samba version is 4.17.0 through 4.17.9, or 4.18.0 through 4.18.4, AND the server has 'server signing = required' configured OR acts as a Domain Controller.

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 4.17.10 / 4.18.5 or later
Fixed in 4.17.104.18.5
Interim mitigation

Ensure Samba installations are updated to versions that enforce SMB2 packet signing as specified in configuration. Verify that 'server signing = required' is properly enforced and monitor for configuration drift.

Recommended fix High confidence

Samba 4.17.10 or later in the 4.17.x series; Samba 4.18.5 or later in the 4.18.x series

  1. Identify the current Samba version installed using 'rpm -qa | grep samba' or 'samba --version'
  2. For RHEL/CentOS/RHEL AMS systems: Run 'dnf update samba' or 'yum update samba' to apply the latest available packages which include the security fix
  3. For Fedora systems: Run 'dnf update samba' to update to the fixed version
  4. For Standalone Samba installations: Download and install Samba 4.17.10 or later, or 4.18.5 or later from the official Samba website (www.samba.org)
  5. After updating, verify the new version with 'samba --version' to confirm the patch was applied
  6. Restart Samba services ('systemctl restart smb nmb') for the changes to take effect
  7. Verify that 'server signing = required' is set in smb.conf if SMB2 packet signing is required for your environment
Caveat Upgrading Samba may require configuration review; ensure custom smb.conf settings are compatible with the new version and test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Storage Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2023-3347 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data