Cisco IOS Common Industrial Protocol (CIP) Remote Denial of Service Vulnerability (CVE-2017-12233)
Executive & SecOps Summary
SECOPS ASSESSMENTCisco IOS Software versions 12.4 through 15.6 with the Common Industrial Protocol (CIP) feature enabled.
An unauthenticated, remote attacker can cause the affected device to reload, resulting in a complete Denial of Service (DoS) condition.
Apply official Cisco software updates or implement Infrastructure Access Control Lists (iACLs) to restrict unauthorized CIP traffic.
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 Center. Below is an example of upgrading the IOS image via TFTP:
! Download and apply the recommended fixed IOS image
Router# copy tftp: flash:
Address or name of remote host? 192.168.1.100
Source filename? c3900e-universalk9-mz.SPA.156-3.M10.bin
Destination filename [c3900e-universalk9-mz.SPA.156-3.M10.bin]?
! Modify boot system path and save configuration
Router(config)# no boot system
Router(config)# boot system flash c3900e-universalk9-mz.SPA.156-3.M10.bin
Router(config)# exit
Router# write memory
Router# reload2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, implement an Infrastructure Access Control List (iACL) to block unauthorized CIP traffic destined to the device.
! Define ACL to permit trusted hosts and deny all other CIP traffic
Router(config)# ip access-list extended BLOCK_CIP_EXPLOIT
Router(config-ext-nacl)# permit tcp 10.100.1.0 0.0.0.255 any eq 44818
Router(config-ext-nacl)# permit udp 10.100.1.0 0.0.0.255 any eq 2222
Router(config-ext-nacl)# deny tcp any any eq 44818
Router(config-ext-nacl)# deny udp any any eq 2222
Router(config-ext-nacl)# permit ip any any
Router(config-ext-nacl)# exit
! Apply ACL to the external interface
Router(config)# interface GigabitEthernet0/0
Router(config-if)# ip access-group BLOCK_CIP_EXPLOIT in
Router(config-if)# exit3. Log Audit & IoC Verification Commands
Verify the current running IOS version and inspect system logs for unexpected reloads.
! Check current running IOS version and uptime
Router# show version | include Software|uptime
! Check if CIP ports are active on the device
Router# show sockets | include 44818|2222
! Inspect logs for unexpected reload reasons
Router# show version | include last reload
Router# show log | include %SYSTEM-3-LOG|%SYS-2-REBOOTStop 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-2017-12233) exists in the Common Industrial Protocol (CIP) parsing implementation of Cisco IOS Software. Due to improper validation of input data (CWE-20) within crafted CIP packets, the parsing engine fails to handle malformed structures safely. This leads to memory reference violations or kernel panics, causing the affected device to unexpectedly crash and reload.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by sending specially crafted CIP packets to an affected device listening on CIP-related ports (typically TCP/UDP 44818 or UDP 2222). Because the vulnerability is pre-authentication and requires no user interaction (AV:N/AC:L/PR:N/UI:N), an attacker can easily trigger a device reload remotely, disrupting network operations without any credentials.
3. Infrastructure & Business Impact
As this vulnerability is listed on the CISA KEV (Known Exploited Vulnerabilities) catalog, it has been actively exploited in the wild. In Industrial Control Systems (ICS/OT) or enterprise backbone environments, a sudden reload of a core Cisco router or switch can lead to significant network downtime, loss of control telemetry, and severe disruption to business-critical operations.
Official Vendor Advisories & References
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: CSCuz95334.
Frequently Asked SecOps Questions (CVE-2017-12233)
FAQQ1. How critical is CVE-2017-12233 and is it actively exploited in the wild?
CVE-2017-12233 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-2017-12233?
Primary impacted vendors include cisco across ios. Scope summary: Cisco IOS Software releases 12.4 through 15.6 configured with the CIP feature (Cisco Bug ID: CSCuz95334).
Q3. What temporary mitigations or workarounds exist for CVE-2017-12233 before patching?
[Mitigation] Apply official Cisco software updates or implement Infrastructure Access Control Lists (iACLs) to restrict unauthorized CIP traffic. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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