dbcve.org
FreeBSDOperating system

CVE-2011-2393

HIGH · 7.8 CVSS v2.0 Published 2012-02-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
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
The Neighbor Discovery (ND) protocol implementation in the IPv6 stack in FreeBSD, NetBSD, and possibly other BSD-based operating systems allows remote attackers to cause a denial of service (CPU consumption and device hang) by sending many Router Advertisement (RA) messages with different source addresses, a similar vulnerability to CVE-2010-4670.

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

The Neighbor Discovery (ND) protocol implementation in the IPv6 stack in FreeBSD, NetBSD, and other BSD-based systems contains a denial of service vulnerability. Remote attackers can send numerous Router Advertisement (RA) messages with varying source addresses, causing excessive CPU consumption and device hang. This exploits how the system processes inbound RA messages.

MitigationRate-limit or filter inbound Router Advertisement messages at network boundaries using firewall rules, disable IPv6 routing features if not required, and apply vendor patches when available for affected BSD systems.

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
FreeBSDOperating system
Affected:all versions
NetbsdOperating system
Affected:all versions

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
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:L/Au:N/C:N/I:N/A:C

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 the operating system
    Run 'uname -a' or check /etc/os-release to confirm the system is FreeBSD or NetBSD
    Affected if The system is running FreeBSD or NetBSD with IPv6 enabled and is receiving Router Advertisement messages on the network interface
  2. Verify IPv6 is enabled
    Check for active IPv6 interfaces using 'ifconfig -a' or 'ip -6 addr show'
    Affected if IPv6 is active and the system has an IPv6 address assigned to any interface
  3. Check for inbound Router Advertisement traffic
    Monitor network traffic using 'tcpdump -i <interface> -vv ip6' to observe incoming RA messages (ICMPv6 type 134)
    Affected if The system is receiving ICMPv6 Router Advertisement packets on any active interface
  4. Look for CPU consumption from nd6 process
    Monitor system CPU usage with 'top' or 'ps aux' and look for unusually high CPU usage from network processing daemons or kernel tasks related to neighbor discovery
    Affected if CPU usage spikes correlate with inbound RA message processing, which may indicate the vulnerability is being triggered
  5. Check for kernel patch status
    Review system logs or vendor security advisories for the specific patch addressing CVE-2011-2393, or compare the kernel version against known patched versions
    Affected if The running kernel is an unpatched version of FreeBSD or NetBSD that has not received the CVE-2011-2393 fix

A defender is affected if they are running an unpatched FreeBSD or NetBSD system with IPv6 enabled and receiving Router Advertisement messages on the network, as the vulnerability exploits the ND protocol processing to cause CPU exhaustion.

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

Rate-limit or filter inbound Router Advertisement messages at network boundaries using firewall rules, disable IPv6 routing features if not required, and apply vendor patches when available for affected BSD systems.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2011-2393 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2011-2393 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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