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iOSOperating system · Cisco

CVE-2018-0163

MEDIUM · 6.5 CVSS v3.1 Published 2018-03-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
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 vulnerability in the 802.1x multiple-authentication (multi-auth) feature of Cisco IOS Software could allow an unauthenticated, adjacent attacker to bypass the authentication phase on an 802.1x multi-auth port. The vulnerability is due to a logic change error introduced into the code. An attacker could exploit this vulnerability by trying to access an 802.1x multi-auth port after a successful supplicant has authenticated. An exploit could allow the attacker to bypass the 802.1x access controls and obtain access to the network. Cisco Bug IDs: CSCvg69701.

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 logic error in Cisco IOS Software's 802.1x multi-authentication feature allows an unauthenticated, adjacent attacker to bypass authentication on an 802.1x multi-auth port by accessing it after a legitimate supplicant has successfully authenticated. This grants the attacker network access without proper 802.1x credentials.

MitigationApply the Cisco IOS software update addressing CSCvg69701. Until patching is feasible, consider temporarily using single-auth mode, implementing complementary controls like port security or MACsec, or leveraging network segmentation to limit exposure.

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
iOSOperating system
Affected:= 15.4\(3\)m6= 15.4\(3\)m6a= 15.4\(3\)m7= 15.4\(3\)m7a= 15.4\(3\)m8= 15.4\(3.0i\)m6= 15.5\(3\)m3= 15.5\(3\)m4= 15.5\(3\)m4a= 15.5\(3\)m4b= 15.5\(3\)m4c= 15.5\(3\)m5

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:A/AC:L/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. Determine the Cisco IOS version
    Run the command 'show version' or 'show version | include IOS' to retrieve the installed IOS version
    Affected if The version matches one of the affected releases: 15.4(3)M6, 15.4(3)M6a, 15.4(3)M7, 15.4(3)M7a, 15.4(3)M8, 15.4(3.0i)M6, 15.5(3)M3, 15.5(3)M4, 15.5(3)M4a, 15.5(3)M4b, or 15.5(3)M5
  2. Identify interfaces with 802.1x authentication enabled
    Run 'show dot1x all' or 'show running-config | include dot1x' to see if 802.1x is configured on any interface
    Affected if 802.1x authentication is enabled on any interface in the configuration
  3. Verify if multi-auth mode is configured on 802.1x interfaces
    Run 'show dot1x interface' or examine the interface configuration with 'show running-config interface <interface>' to check for 'authentication port-control auto' combined with multi-auth mode settings
    Affected if The interface is configured with multi-authentication mode (typically via 'authentication multi-auth' or similar multi-auth configuration)
  4. Check for the specific vulnerable configuration pattern
    Review the interface configuration for 802.1x with multi-auth mode enabled. Look for 'dot1x pae authenticator' and 'authentication multi-auth' in the interface or global dot1x configuration
    Affected if 802.1x multi-auth mode is active on a port and the IOS version matches the affected versions list

You are affected if your Cisco IOS version matches one of the listed affected versions AND you have 802.1x multi-authentication mode configured on any interface.

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

Apply the Cisco IOS software update addressing CSCvg69701. Until patching is feasible, consider temporarily using single-auth mode, implementing complementary controls like port security or MACsec, or leveraging network segmentation to limit exposure.

Fix this in iOS 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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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-2018-0163 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