Cisco IOS and IOS XE Autonomic Networking Denial of Service Vulnerability (CVE-2017-6663)
Executive & SecOps Summary
SECOPS ASSESSMENTCisco network devices running Cisco IOS or IOS XE Software with the Autonomic Networking feature enabled (specifically Denali-16.2.1, Denali-16.3.1)
An unauthenticated, adjacent attacker can cause affected autonomic nodes to reload, leading to a complete Denial of Service (DoS) condition
Apply official Cisco software updates or disable the Autonomic Networking Infrastructure (ANI) feature if not required
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade to a patched Cisco IOS/IOS XE release via TFTP/SFTP. Below is an example of upgrading the boot image:
! Copy the patched IOS XE image from the file server
copy tftp://10.1.1.100/cat3k_caa-universalk9.16.03.02.SPA.bin flash:
configure terminal
boot system switch all flash:cat3k_caa-universalk9.16.03.02.SPA.bin
end
write memory
reload2. Temporary Workaround & Hardening Configuration
If patching cannot be scheduled immediately, disable the Autonomic Networking feature globally to mitigate the threat vector:
! Disable Autonomic Networking Infrastructure globally
configure terminal
no autonomic-networking
end
write memory3. Log Audit & IoC Verification Commands
Verify whether the Autonomic Networking feature is active and inspect system logs for unexpected reloads:
! Check the status of Autonomic Networking
show autonomic device info
! Inspect reload history and system crash logs
show version | include uptime|System returned
show logging | include %SYS-2-RELOAD|%AN-statusStop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
Eliminate public-facing VPN concentrators and firewall management ports with identity-first Zero-Trust Network Access.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
A vulnerability in the Autonomic Networking feature of Cisco IOS Software and Cisco IOS XE Software allows an unauthenticated, adjacent attacker to trigger a system reload. The root cause lies in the improper validation of incoming Autonomic Networking Infrastructure (ANI) control packets, leading to an unhandled exception and subsequent kernel panic when processing malformed inputs.
2. Exploitation Mechanics & Attack Scenario
To exploit this vulnerability, an attacker must be located on the same Layer 2 network or be adjacent to the target device. By transmitting crafted autonomic networking packets directly to an active ANI-enabled interface, the attacker triggers a parsing anomaly. This causes the device's control plane to crash and reload immediately without requiring any administrative credentials.
3. Infrastructure & Business Impact
This vulnerability is listed in the CISA KEV catalog, indicating active exploitation history. A successful exploit can lead to a continuous loop of device reloads if the attacker persists, resulting in a complete loss of network routing capabilities, service degradation, and severe business disruption.
Official Vendor Advisories & References
A vulnerability in the Autonomic Networking feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause autonomic nodes of an affected system to reload, resulting in a denial of service (DoS) condition. More Information: CSCvd88936. Known Affected Releases: Denali-16.2.1 Denali-16.3.1.
Frequently Asked SecOps Questions (CVE-2017-6663)
FAQQ1. How critical is CVE-2017-6663 and is it actively exploited in the wild?
CVE-2017-6663 is rated CVSS 6.5 (MEDIUM) with a 30-day EPSS exploitation probability of 2.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2017-6663?
Primary impacted vendors include cisco across ios, ios_xe. Scope summary: Cisco IOS and IOS XE Software with Autonomic Networking enabled. Known affected releases include Denali-16.2.1 and Denali-16.3.1.
Q3. What temporary mitigations or workarounds exist for CVE-2017-6663 before patching?
[Mitigation] Apply official Cisco software updates or disable the Autonomic Networking Infrastructure (ANI) feature if not required Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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