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Ubuntu LinuxOperating system · Canonical

CVE-2018-1139

HIGH · 8.1 CVSS v3.1 Published 2018-08-22
Fix available
A fix is available. Upgrade to 4.7.9 / 4.8.4 or later.
See remediation →
90/100
Remediation priority · Urgent
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 way samba before 4.7.9 and 4.8.4 allowed the use of weak NTLMv1 authentication even when NTLMv1 was explicitly disabled. A man-in-the-middle attacker could use this flaw to read the credential and other details passed between the samba server and client.

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 vulnerability in Samba versions before 4.7.9 and 4.8.4 allowed weak NTLMv1 authentication to be used even when explicitly disabled in configuration. A man-in-the-middle attacker could exploit this to intercept and read credentials and other sensitive data transmitted between the Samba server and clients.

MitigationUpgrade Samba to version 4.7.9 or later, or 4.8.4 or later, and verify that NTLMv1 is properly disabled and NTLMv2 authentication functions correctly after the update.

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
Ubuntu LinuxOperating system
Affected:= 14.04= 16.04= 18.04
Enterprise Linux DesktopOperating system
Affected:= 7.0
Enterprise Linux ServerOperating system
Affected:= 7.0
Enterprise Linux WorkstationOperating system
Affected:= 7.0
SambaApplication
Affected:>= 4.7.0, < 4.7.9>= 4.8.0, < 4.8.4

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/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. Identify installed Samba version
    Run 'smbd --version' or 'rpm -q samba' (RHEL) or 'dpkg -l | grep samba' (Ubuntu) to retrieve the installed Samba version number
    Affected if Version is 4.7.0 through 4.7.8, or 4.8.0 through 4.8.3
  2. Confirm Ubuntu version if applicable
    Run 'lsb_release -a' or check '/etc/lsb-release' to identify the Ubuntu distribution version
    Affected if Running Ubuntu 14.04, 16.04, or 18.04 with Samba installed from packages
  3. Confirm RHEL version if applicable
    Run 'cat /etc/redhat-release' to identify the Red Hat Enterprise Linux version
    Affected if Running RHEL 7.0 with Samba installed
  4. Locate Samba configuration file
    Check for '/etc/samba/smb.conf' or the path specified in 'testparm -s' output to locate the active smb.conf
    Affected if Configuration file exists and Samba is running as a server
  5. Check NTLMv1 authentication settings
    In smb.conf, search for 'ntlm auth =' or 'lanman auth =' settings. Run 'testparm -v | grep -i ntlm' to see current effective values
    Affected if Configuration shows 'ntlm auth = disabled' or 'lanman auth = No' but NTLMv1 may still be accepted due to the vulnerability
  6. Verify NTLM authentication behavior
    Attempt a connection from a client using NTLMv1. Check Samba server logs (typically /var/log/samba/) for 'NTLMv1' authentication events, or use network capture to observe the NTLMSSP negotiation
    Affected if NTLMv1 authentication succeeds despite 'ntlm auth = disabled' being set in configuration

The environment is affected if Samba version is between 4.7.0 and 4.7.8, or between 4.8.0 and 4.8.3, or if running the specified Ubuntu/RHEL versions with Samba installed, and NTLMv1 is accepted even when explicitly disabled in smb.conf.

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 4.7.9 / 4.8.4 or later
Fixed in 4.7.94.8.4
Interim mitigation

Upgrade Samba to version 4.7.9 or later, or 4.8.4 or later, and verify that NTLMv1 is properly disabled and NTLMv2 authentication functions correctly after the update.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2018-1139 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