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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-2017-12234

HIGH · 7.5 CVSS v3.1 Published 2017-09-29
Fix available
A fix is available. Upgrade to after 15.6 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild 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
Multiple vulnerabilities in the implementation of the Common Industrial Protocol (CIP) feature in Cisco IOS 12.4 through 15.6 could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerabilities are due to the improper parsing of crafted CIP packets destined to an affected device. An attacker could exploit these vulnerabilities by sending crafted CIP packets to be processed by an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCvc43709.

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

Multiple vulnerabilities in Cisco IOS versions 12.4 through 15.6 allow an unauthenticated remote attacker to cause denial of service by sending specially crafted Common Industrial Protocol (CIP) packets to an affected device. The vulnerability stems from improper parsing of CIP packets destined to the device, which when successfully exploited causes the device to reload.

MitigationApply the Cisco security update for CSCvc43709 to the affected IOS devices. If patches are unavailable, restrict network access to CIP-enabled interfaces or implement firewall rules to filter untrusted CIP traffic.

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:>= 12.4, <= 15.6

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
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/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. Determine IOS version
    Run 'show version' or 'show ios version' on the device to retrieve the installed Cisco IOS version
    Affected if The version falls within >= 12.4 and <= 15.6
  2. Verify CIP protocol is enabled
    Check the device configuration for CIP-related commands using 'show running-config | include cip' or 'show ip interface' to see if Common Industrial Protocol is configured
    Affected if CIP protocol is enabled or configured on any interface
  3. Identify CIP-enabled interfaces
    Review interface configurations for CIP settings using 'show running-config' and look for cip-related interface parameters or CIP-enabled VLANs
    Affected if Any interface has CIP explicitly enabled or bound
  4. Check CIP service listeners
    Use 'show cip status' or 'show cip interface' if available to confirm the CIP service is actively listening
    Affected if The CIP service is running and accepting connections
  5. Assess network exposure
    Review access control lists and interface IP addresses to determine if CIP-enabled interfaces are reachable from untrusted networks
    Affected if CIP-enabled interfaces are externally accessible or have minimal firewall protection

The device is affected if it runs Cisco IOS version 12.4 through 15.6 AND has CIP protocol enabled on any accessible interface, making it vulnerable to specially crafted CIP packets causing device reload.

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 15.6
Interim mitigation

Apply the Cisco security update for CSCvc43709 to the affected IOS devices. If patches are unavailable, restrict network access to CIP-enabled interfaces or implement firewall rules to filter untrusted CIP traffic.

Fix this in iOS Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation20.0 h
  • Testing16.0 h
  • Review / QA4.0 h
44.0 hours of engineering $7,520
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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-2017-12234 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