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Network Access ControlOperating system · Cisco

CVE-2006-4983

HIGH · 7.5 CVSS v2.0 Published 2006-09-26
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
Cisco NAC allows quarantined devices to communicate over the network with (1) DNS, (2) DHCP, and (3) EAPoUDP, which allows attackers to bypass control methods by tunneling network traffic through one of these protocols.

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

Cisco NAC (Network Access Control) was found to improperly allow quarantined devices to continue communicating over the network using DNS, DHCP, and EAPoUDP protocols. This design flaw allowed attackers to bypass NAC quarantine controls by tunneling malicious traffic through these typically trusted protocols, effectively circumventing the security posture enforcement intended by NAC.

MitigationOrganizations should implement additional network segmentation and firewall rules to explicitly block DNS, DHCP, and EAPoUDP traffic from quarantined VLANs, or migrate to updated NAC solutions that properly restrict all traffic from non-compliant devices.

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
Network Access ControlOperating 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
Partial
Integrity
Partial
Availability
Partial

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

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. Confirm Cisco NAC deployment
    Review network infrastructure documentation or check for Cisco NAC appliances/controllers on the network. Look for NAC servers, agents, or inline enforcement devices.
    Affected if Cisco Network Access Control is implemented in the environment
  2. Identify quarantine VLAN configuration
    Check the VLAN assignment for devices flagged as quarantined or non-compliant. In NAC admin console, locate the quarantine policy/VLAN settings.
    Affected if A separate quarantine VLAN or policy exists for non-compliant devices
  3. Verify DNS traffic filtering from quarantine
    From a quarantined device or test system in the quarantine VLAN, attempt to resolve external DNS queries or capture traffic to confirm if UDP port 53 to external DNS servers is allowed.
    Affected if DNS queries to external resolvers succeed from quarantine zone
  4. Verify DHCP traffic handling in quarantine
    Check if DHCP requests from quarantine VLAN can reach external DHCP servers, or if relay agents forward DHCP to external infrastructure.
    Affected if DHCP traffic from quarantine can reach servers outside the isolated network
  5. Check EAPoUDP protocol restrictions
    Examine firewall or access control rules between quarantine VLAN and trusted networks. Determine if UDP port 2552555 (EAPoUDP) is permitted to flow from quarantined devices to non-NAC infrastructure.
    Affected if EAPoUDP protocol is allowed beyond NAC enforcement points to external networks

The environment is affected if Cisco NAC is deployed and any of DNS, DHCP, or EAPoUDP protocols are permitted to pass from quarantine zones to external or trusted networks without explicit blocking.

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

Organizations should implement additional network segmentation and firewall rules to explicitly block DNS, DHCP, and EAPoUDP traffic from quarantined VLANs, or migrate to updated NAC solutions that properly restrict all traffic from non-compliant devices.

Fix this in Network Access Control Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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Scan for this in your stack

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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-2006-4983 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
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