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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 24 Mar 2022.
iOSOperating system · Cisco

CVE-2017-12238

MEDIUM · 6.5 CVSS v3.1 Published 2017-09-29
Fix available
A fix is available. Upgrade to after 15.4 or later.
See remediation →
99/100
Remediation priority · Urgent
In the wild 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 Virtual Private LAN Service (VPLS) code of Cisco IOS 15.0 through 15.4 for Cisco Catalyst 6800 Series Switches could allow an unauthenticated, adjacent attacker to cause a C6800-16P10G or C6800-16P10G-XL type line card to crash, resulting in a denial of service (DoS) condition. The vulnerability is due to a memory management issue in the affected software. An attacker could exploit this vulnerability by creating a large number of VPLS-generated MAC entries in the MAC address table of an affected device. A successful exploit could allow the attacker to cause a C6800-16P10G or C6800-16P10G-XL type line card to crash, resulting in a DoS condition. This vulnerability affects Cisco Catalyst 6800 Series Switches that are running a vulnerable release of Cisco IOS Software and have a Cisco C6800-16P10G or C6800-16P10G-XL line card in use with Supervisor Engine 6T. To be vulnerable, the device must also be configured with VPLS and the C6800-16P10G or C6800-16P10G-XL line card needs to be the core-facing MPLS interfaces. Cisco Bug IDs: CSCva61927.

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 memory management flaw in the VPLS (Virtual Private LAN Service) code of Cisco IOS 15.0-15.4 on Catalyst 6800 Series Switches allows an adjacent, unauthenticated attacker to crash specific line cards (C6800-16P10G or C6800-16P10G-XL) by flooding the MAC address table with VPLS-generated entries, causing a denial of service.

MitigationUpgrade Cisco IOS to a fixed version per CSCva61927, or implement MAC address table limits on VPLS interfaces and verify line card configurations to reduce attack surface.

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:>= 15.0, <= 15.4

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
None
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/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. Identify device model
    Run 'show version' or 'show module' to confirm the device is a Cisco Catalyst 6800 Series Switch
    Affected if Device is a Catalyst 6800 Series Switch
  2. Check Cisco IOS version
    Run 'show version' and locate the IOS version number. Compare it against the 15.0 to 15.4 range.
    Affected if IOS version falls between 15.0 and 15.4 inclusive
  3. Verify VPLS configuration
    Run 'show vpls' or 'show run | include vpls' to check if VPLS (Virtual Private LAN Service) is configured on any interface
    Affected if VPLS is configured and active on the device
  4. Identify line card hardware
    Run 'show inventory' or 'show module' to list installed line cards and identify if C6800-16P10G or C6800-16P10G-XL are present
    Affected if One or both of the affected line card models (C6800-16P10G or C6800-16P10G-XL) are installed

All four conditions must be true: Catalyst 6800 Series Switch, IOS 15.0-15.4, VPLS configured, and affected line card present.

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
Upgrade available Upgrade to a release after 15.4
Interim mitigation

Upgrade Cisco IOS to a fixed version per CSCva61927, or implement MAC address table limits on VPLS interfaces and verify line card configurations to reduce attack surface.

Fix this in iOS Exploited in the wild — priority engagement
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  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
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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-2017-12238 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