dbcve.org
FedoraOperating system · Fedoraproject

CVE-2020-14303

HIGH · 7.5 CVSS v3.1 Published 2020-07-06
Fix available
A fix is available. Upgrade to 4.10.17 / 4.11.11 or later.
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 AD DC NBT server in all Samba versions before 4.10.17, before 4.11.11 and before 4.12.4. A samba user could send an empty UDP packet to cause the samba server to crash.

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 denial of service vulnerability exists in Samba's Active Directory Domain Controller (AD DC) NBT (NetBIOS over TCP/IP) server. An attacker can send an empty UDP packet to the NBT server listening on port 137, causing the Samba server to crash. This affects all Samba versions prior to 4.10.17, 4.11.11, and 4.12.4.

MitigationUpgrade Samba to version 4.10.17 or later, 4.11.11 or later, or 4.12.4 or later. Alternatively, if immediate upgrade is not possible, consider blocking external access to UDP port 137 at the network perimeter.

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
FedoraOperating system
Affected:= 31
Debian LinuxOperating system
Affected:= 9.0
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 16.04= 18.04= 20.04
SambaApplication
Affected:>= 4.10.0, < 4.10.17>= 4.11.0, < 4.11.11>= 4.12.0, < 4.12.4
LeapOperating system
Affected:= 15.1= 15.2

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. Verify Samba is installed
    Run 'smbd --version' or 'rpm -q samba' (RHEL/Fedora) or 'dpkg -l | grep samba' (Debian/Ubuntu)
    Affected if Samba is not installed, the system is not affected by this specific vulnerability
  2. Confirm the installed Samba version
    Compare the version output from 'smbd --version' against the affected ranges: 4.10.0 to 4.10.16, 4.11.0 to 4.11.10, or 4.12.0 to 4.12.3
    Affected if The version falls within any of these ranges (less than 4.10.17, 4.11.11, or 4.12.4)
  3. Determine if the NBT (NetBIOS) service is enabled and running
    Run 'systemctl status nmb' or check if port 137/UDP is open with 'ss -ulnp | grep :137' or 'netstat -ulnp | grep :137'
    Affected if The nmbd service is running and listening on UDP port 137, making the NBT server exploitable
  4. Check if Samba is configured as an Active Directory Domain Controller
    Examine the smb.conf file (typically at /etc/samba/smb.conf) for 'server role = active directory domain controller' under the [global] section
    Affected if Samba is configured as an AD DC, which is the specific component affected by this vulnerability

A system is affected if it runs a vulnerable Samba version (below 4.10.17, 4.11.11, or 4.12.4) with the NBT server enabled and configured as an AD DC, exposing UDP port 137 to the attacker.

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
Upgrade available Upgrade to 4.10.17 / 4.11.11 / 4.12.4 or later
Fixed in 4.10.174.11.114.12.4
Interim mitigation

Upgrade Samba to version 4.10.17 or later, 4.11.11 or later, or 4.12.4 or later. Alternatively, if immediate upgrade is not possible, consider blocking external access to UDP port 137 at the network perimeter.

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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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-2020-14303 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