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LibvirtApplication · Redhat

CVE-2016-5008

CRITICAL · 9.8 CVSS v3.0 Published 2016-07-13
Fix available
A fix is available. Upgrade to after 1.3.5 or later.
See remediation →
100/100
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
libvirt before 2.0.0 improperly disables password checking when the password on a VNC server is set to an empty string, which allows remote attackers to bypass authentication and establish a VNC session by connecting to the server.

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

libvirt before 2.0.0 contains a critical authentication bypass flaw in its VNC server implementation. When a VNC password is configured as an empty string, libvirt incorrectly disables password verification entirely rather than rejecting the empty password, allowing any remote attacker to connect to the VNC session without any authentication.

MitigationUpgrade libvirt to version 2.0.0 or later, and ensure VNC server configurations never use empty passwords. Audit all existing libvirt deployments for VNC configurations using blank passwords.

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
LibvirtApplication
Affected:<= 1.3.5
Debian LinuxOperating system
Affected:= 8.0

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:3.0/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 installed libvirt version
    Run 'rpm -q libvirt' (RHEL) or 'dpkg -l libvirt' (Debian) to get the installed version number, then compare it to the affected range (versions below 2.0.0, specifically <= 1.3.5 for Red Hat)
    Affected if The installed version is less than 2.0.0 (or 1.3.5 or earlier on Red Hat systems)
  2. Identify active VNC server configurations
    Search libvirt configuration files in /etc/libvirt/ for '<graphics type='vnc'' entries, or use 'virsh domdisplay <domain>' to check which domains have VNC graphics enabled
    Affected if Any virtual machine is configured with VNC graphics type (not SPICE or other)
  3. Inspect VNC password settings
    Examine the VNC graphics configuration in the domain XML (via 'virsh dumpxml <domain>') for a '<password>' element, or check /etc/libvirt/qemu/*.xml files for the password attribute under <graphics>
    Affected if The VNC password is set to an empty string (password='' or no password element present when one is expected)
  4. Verify password enforcement
    Review libvirt daemon configuration (/etc/libvirt/libvirtd.conf) for 'vnc_password' setting, and check if the VNC server is bound to all interfaces (listen='0.0.0.0') making it network-accessible
    Affected if The VNC server allows passwordless access or binds to a reachable network address without proper authentication

You are affected if libvirt version is below 2.0.0 and any virtual machine has VNC enabled with an empty or missing password configuration, allowing unauthenticated remote access.

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 a release after 1.3.5
Interim mitigation

Upgrade libvirt to version 2.0.0 or later, and ensure VNC server configurations never use empty passwords. Audit all existing libvirt deployments for VNC configurations using blank passwords.

Recommended fix High confidence

libvirt 2.0.0 or later

  1. Check current libvirt version using 'rpm -q libvirt' (RHEL/CentOS) or 'dpkg -l libvirt' (Debian)
  2. For Debian 8.0: Run 'apt-get update && apt-get install libvirt' to apply security updates, or check for available updates via 'apt-cache policy libvirt'
  3. For RHEL/CentOS: Run 'yum update libvirt' or 'rpm -Uvh' for the specific fixed package
  4. After upgrade, restart the libvirt service: 'systemctl restart libvirtd' (or 'service libvirtd restart' on older systems)
  5. Verify the new version is >= 2.0.0 using 'libvirtd --version'
Caveat Review libvirt 2.0.0 release notes for any API or configuration changes that may affect existing setups

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

Fix this in Libvirt Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,800
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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-2016-5008 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