Cisco IOS PROFINET PN-DCP Packet Processing Remote Denial of Service Vulnerability (CVE-2017-12235)
Executive & SecOps Summary
SECOPS ASSESSMENTCisco devices running Cisco IOS Software releases 12.2 through 15.6 configured to process PROFINET messages.
An unauthenticated, remote attacker can cause the affected device to reload, resulting in a persistent Denial of Service (DoS) condition.
Apply official Cisco IOS software updates, or disable the PROFINET protocol if it is not required in your environment.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade to a fixed Cisco IOS Software release via the Cisco Software Central.
! Download the secure IOS image from TFTP server and set boot path
copy tftp: flash:
Address or name of remote host? 192.168.1.100
Source filename? c2960x-universalk9-mz.152-7.E8.bin
Destination filename [c2960x-universalk9-mz.152-7.E8.bin]?
configure terminal
boot system flash:/c2960x-universalk9-mz.152-7.E8.bin
end
write memory
reload2. Temporary Workaround & Hardening Configuration
If patching cannot be applied immediately, disable PROFINET globally or restrict access using Access Control Lists (ACLs).
! Disable PROFINET globally
configure terminal
no profinet
end
write memory
! Alternatively, block PN-DCP traffic using an ACL
configure terminal
ip access-list extended BLOCK_PROFINET
deny udp any any eq 34964
permit ip any any
interface GigabitEthernet0/1
ip access-group BLOCK_PROFINET in
end
write memory3. Log Audit & IoC Verification Commands
Verify the current IOS version, check if PROFINET is active, and inspect system logs for unexpected reloads.
! Check IOS version and PROFINET status
show version | include Software
show profinet status
! Inspect logs for abnormal reload signatures
show version | include returned to rom
show logging | include %SYSTEM-3-RSTStop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2017-12235) exists in the implementation of the PROFINET Discovery and Configuration Protocol (PN-DCP) parser within Cisco IOS Software. The root cause is improper input validation (CWE-20) of ingress PN-DCP Identify Request packets destined to an affected device. When the device processes a malformed packet, it fails to handle the parsing exception correctly, leading to a kernel panic and an unexpected system reload.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by sending a specially crafted PN-DCP Identify Request packet to an affected Cisco device, followed by a sequence of normal PN-DCP Identify Request packets. Because the vulnerability is triggered during the parsing phase of the network stack, no authentication or user interaction is required. This allows remote attackers with network access to easily trigger a device reload, disrupting network traffic.
3. Infrastructure & Business Impact
Starting with Cisco IOS Software Release 12.2(52)SE, PROFINET is enabled by default on all base switch modules and expansion-unit Ethernet ports. This default configuration significantly expands the attack surface, exposing not only Industrial Control Systems (ICS/OT) but also standard enterprise networks. Since this vulnerability is actively exploited in the wild (CISA KEV listed), successful exploitation can lead to cascading network outages, impacting critical business operations and infrastructure availability.
Official Vendor Advisories & References
A vulnerability in the implementation of the PROFINET Discovery and Configuration Protocol (PN-DCP) for Cisco IOS 12.2 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 vulnerability is due to the improper parsing of ingress PN-DCP Identify Request packets destined to an affected device. An attacker could exploit this vulnerability by sending a crafted PN-DCP Identify Request packet to an affected device and then continuing to send normal PN-DCP Identify Request packets to the device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. This vulnerability affects Cisco devices that are configured to process PROFINET messages. Beginning with Cisco IOS Software Release 12.2(52)SE, PROFINET is enabled by default on all the base switch module and expansion-unit Ethernet ports. Cisco Bug IDs: CSCuz47179.
Frequently Asked SecOps Questions (CVE-2017-12235)
FAQQ1. How critical is CVE-2017-12235 and is it actively exploited in the wild?
CVE-2017-12235 is rated CVSS 7.5 (HIGH) with a 30-day EPSS exploitation probability of 7.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2017-12235?
Primary impacted vendors include cisco across ios. Scope summary: Cisco IOS Software releases 12.2 through 15.6 with PROFINET enabled (Cisco Bug ID: CSCuz47179).
Q3. What temporary mitigations or workarounds exist for CVE-2017-12235 before patching?
[Mitigation] Apply official Cisco IOS software updates, or disable the PROFINET protocol if it is not required in your environment. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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