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Ubuntu LinuxOperating system · Canonical

CVE-2011-4600

MEDIUM · 5.9 CVSS v3.0 Published 2016-04-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
The networkReloadIptablesRules function in network/bridge_driver.c in libvirt before 0.9.9 does not properly handle firewall rules on bridge networks when libvirtd is restarted, which might allow remote attackers to bypass intended access restrictions via a (1) DNS or (2) DHCP query.

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

In libvirt before 0.9.9, the networkReloadIptablesRules function in bridge_driver.c fails to properly restore firewall rules when libvirtd restarts. This leaves bridge networks with incorrect or missing iptables rules, potentially allowing remote attackers to bypass access restrictions through DNS or DHCP queries.

MitigationUpgrade libvirt to version 0.9.9 or later where the rule reloading is fixed. Alternatively, manually verify and reapply iptables rules for bridge networks after any libvirtd restart.

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:= 12.04= 14.04= 15.04= 15.10
LibvirtApplication
Affected:= 0.9.8

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:3.0/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 libvirt version
    Run 'libvirtd --version' or 'rpm -q libvirt' (Red Hat) or 'dpkg -l libvirt-bin' (Ubuntu) to determine the installed version
    Affected if Version is 0.9.8 or lower (below 0.9.9)
  2. Verify bridge networks are configured
    Run 'virsh net-list --all' to list all network definitions, look for networks with bridge='yes' or network type='bridge'
    Affected if Any active bridge network exists in the environment
  3. Check if libvirtd has been restarted
    Review system logs (journalctl -u libvirtd or /var/log/libvirt/libvirtd.log) for restart events, or run 'systemctl status libvirtd' to check service status
    Affected if Libvirtd service has been restarted since bridge networks were configured
  4. Inspect iptables rules for bridge interfaces
    Run 'iptables -L -v -n' or 'iptables -S' to list current iptables rules, then use 'ip link show' to identify bridge interfaces (virbr0, etc.) and check if corresponding INPUT/FORWARD rules exist for those bridges
    Affected if Rules are missing or incorrect for bridge interfaces (e.g., no ACCEPT rules for the bridge traffic when they should exist)
  5. Compare version against known affected ranges
    Based on the version found in step 1, compare against: Ubuntu 12.04, 14.04, 15.04, 15.10 or Red Hat libvirt 0.9.8
    Affected if Running Ubuntu 12.04/14.04/15.04/15.10 or Red Hat libvirt 0.9.8 specifically, or any version below 0.9.9

You are affected if you are running libvirt version 0.9.8 or lower, have bridge networks configured, and libvirtd has been restarted since those networks were set up, resulting in missing or incorrect iptables rules for your bridge interfaces.

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

Upgrade libvirt to version 0.9.9 or later where the rule reloading is fixed. Alternatively, manually verify and reapply iptables rules for bridge networks after any libvirtd restart.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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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-2011-4600 in production — separate from our analysis above.

No notes yet

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What this is

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What belongs here
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